I am going to try and be non judgemental here, but please hear me out...

Why are you with a man who feels like it is totally cool to have 2 kids with you, live with you, have you take care of his previous kid, but doesn't see you as "marriage material"?

Honestly, I know you just had a baby, but start looking at your exit plan. I could never be with someone who just demanded of me and didn't even see the mother of his 2 children as wife worthy. 

To answer your question, you're not the a**hole here.

Hmm......let's see here. He says he doesn't want to marry you yet he expects you to live with him, parent his kids, raise his kids, and even had more children with you. Yet he doesn't view you as wife material? I'm trying not to lose my cool but wow! What a selfish A hole. I'm sorry but also the way he is acting towards you and him going out of town only made me think the worst. Do you think he has met someone else and is having an affair? Also about BM. I don't understand why she doesn't have her child more than she does. Very odd. What's the story behind that? After all she is her parent!!! Why did they divorce? Was he cheating on her? I'm just curious. He sounds like a real gem (sarcasm).

When I have to take care of my steps I don't resent it all. granted it's only EOWE. But my partner would NEVER put me in this situation and he does as much or more taking care of my son as I do his kids. If your boyfriend was pulling his weight in the family, you wouldn't resent the SD. Well, you should never resent the SD - it's not her fault she's alive, but you wouldn't resent the responsibility when it did fall on you. 

Also if it's not BM's week it's not her responsibility (except in extreme cases). Dad's week, dad's problem. But he knows you'll pick up the pieces.

One question though - do you work outside the home (normally maybe not right now)? Because if you don't, it's not completely wrong for a division of labour like this. 

You're not an a-hole.  A lot is being expected of you and it's not your responsibility.  What got me enraged is when you said wrote you are recovering from a C section and he got mad you won't drive her 30 minutes to school.  That's so inconsiderate.  Yes, you did enter a relationship knowing he had a child however that doesn't mean your happiness is sacrificed for everyone else.  I'm sorry.

Just going to reiterate what everyone else has said....2 kids but not "ready" to be married. Get rid of him yesterday and find your self-worth. You sound awesome to me. He should be running to the altar with you, if you'd have him. You won't have to look long or far to find someone who values you instead of using you. Good luck

Agree with others, you sound like a sweet sGirlfriend/StepMom... your BF, not so much. 

Girl!!!!!!  I'm a long time poster here at step talk.  Years.  I was with my DD4's dad for six years. Long time.  He too lived with me.  I had his child on my health insurance.  I supported him financially.  We had DD together.  And then work said his kids couldn't be on my health insurance anymore unless we were married.  Work said we couldn't do the domestic partnership thing anymore and have them on my health insurance because they didnt live with us full time.  My younger SD has type 1 diabetes and she has to have health insurance to survive and it is very expensive.  So he text messaged me and said let's get hitched.  Next week.  It was very unromantic and I was very sad that I got no wedding and no proposal or ring but I was going to go through with it for the SD's health insurance.  And the day before the wedding he starts boo hoo crying.  TEARS.  And he's shaking uncontrollably and says he can't marry me.  Yep.  All those years of me putting up with his crazy ex wife and supporting him and watching his kids.  I wasn't good enough to marry.  And I kicked him out.

And I found this. And I want you to read this.  It was life changing for me.  I've shared it with many people here on step talk and I want you to read it.  https://markmanson.net/love  And I want you to know that I'm doing just fine.  I kicked him out.  I raise my children.  I've been promoted in my career.  Our daughter just turned 4.  He constantly almost monthly sings the "Baby come back... You can blame it all on me... I was wrong.. And I just can't live without you"  song.  But I read that article.  And I have changed.  Love thyself.        Please read it. 

You’re boyfriend sounds like a Grade A a**hole. Just utterly clueless. 

Take your children and live your best life. Without a doubt, there is someone out in the world who will love you and value your worth. 

"Side note: he also doesn’t want to marry me and says we’re not ready and not on the same page but he still wants me to take care of his daughter."

You are behaving reasonably.  Your BF is a complete and total ass.  You're good enough to procreate and serve as the unpaid nanny, but not good enough to marry?  Honey, take that as an invitation to leave his sorry ass and look for someone who truly loves and appreciates you.

This idiot is going to find himself living in a studio apartment eating peaches out of a can because once he pays you child support, he wont have enough money for anything else.

You're not the first poster who found herself being used as BM and BD's unpaid nanny. It's not right, it's not normal, and you are not the A-hole in the equation. Tell him you're never watching his daughter for him again, because he doesnt live there anymore.

Please remove toxic ahole user/losers from your life.  I PROMISE you that will improve your life 100%.

First off, you should NOT be driving for at least SIX WEEKS after a c-section. Get your doc to tell him that in no uncertain terms. Secondly, he is treating you like a maid and a nanny. He's not ready for marriage? Well, of course he isn't. He has a skivvy doing what he wants already (no offence to you intended - I actually admire that you have the balls to fight back ). 

Here's what I'd do. Pack your bags and move out or kick him out if the home is yours. You do not need a millstone round your neck when you have two children  to take care of on your own. His daugher? His problem. And go after his sorry, churlish, jerk of an ass for child support. Never look back and live happily ever after.