I need help to quit living in fear of another custody battle.

Ok-not-so-briefly here is my situation: My DH got custody of his pre-school aged son about a year ago. I did a lot of work, stressing, and pretty much was just as much a part of the battle as he was. I'm emotionaly drained. And not sure I can survive EVER going through that again. We have custody 3/4 of the time. The decision surprised both us and our lawyer (we were expecting full), but we accepted it. Just surprised by the judge.

The worlds between our house and BM's house are opposite. Bio mom is as uncooperative as a person could be sometimes-unpredictable, too. She has a drug history, lost her son because of alcohol and lives in secrecy. We don't even officially know where she lives (and aren't 100% positive, unofficially). She never follows the parenting plan, and has even alluded once that the parenting plan is no longer in place after the custody hearing (it is, just the visitation and a few other responsibilities got swapped). Sometimes, though, she's fine. I am usually good at understanding people, or at least enough to have patience. Totally clueless here. But try to work with it.

We try hard to do things right. My husband used to drink when he was married to her, but quit once he met me. I don't allow it. However, occassionally we like to have a drink or two on special occassions-weddings, birthday parties, etc. My step-son is in a good preschool that he loves, has endless opportunities for fun and learning (I'm a SAHM with him and my baby girl). He's happy here. He loves his mom's house too (thank goodness-that is what we wanted. He hated it when we got custody).

I don't have anything to hide. I feel we provide very well for his son. Yet I am ALWAYS ALWAYS afraid to lose custody. That one little slip-up is going to cost us everything and that I will be a failure. Like I mentioned, the judge surprised us once. I feel like I could do everything perfect and it could all still be taken away. It is ruining my life, to be frank about it.

Lately his son has been throwing horrible tantrums when I pick him up saying he loves mommy and wants to stay with her. But 5 minutes later he is fine and he is happy until the next pickup. We talk about her (in very good ways) and try to encourage their relationship. It still breaks my heart and makes me worry that that will tell the judge he wants to live with her (even though he's very happy and better off here).

I doubt she could ever hire a lawyer. We have enough family support we could. And I believe we could honestly win. I just don't know how to be at peace. I don't know how to quit anticipating the worst. This is what I got and don't know if it is worth it:

Get a really good lawyer now (before anything happens) and get his advice. If something happens (which it always does) we can go through him. Like to find out where she lives.

Hire a PI. Our family friend is a private investigator. He could tell me IF she is still doing the things I think she is that could be used against her. Or tell me she is not and give me peace of mind that if she gets custody back, he'll be ok.

What I really really want is cooperative parenting. No accusations, no confrontations. NO SECRECY - which pretty much negates the two options above! But I don't think she'll ever ever go for it. Can't change people, just how you react!

Any thoughts? What do you do? What should I do?

And yes, I document everything (hubby says he will do this stuff, but never does) and am going to counseling since I am obviously a little paranoid