X's test were all false positives, too. It was the darndest thing- he'd act as if he was on drugs and the tests would say he was on drugs. Go figure.
I think you have to weigh what's scarier- being a single mom of 4, or losing your kids altogether? Because that can happen. It almost happened to me. I remember being so shocked when I put in an anonymous call to CPS and asked what I should do about my ex refusing to go to rehab. They told me if I were to give them my information, they'd come and take my kids. They said no matter how against it I may be, how many ultimatums I'd given him, I was allowing an addict access to my kids, thereby proving myself unfit.
AND EVEN THAT WASN'T ENOUGH TO MAKE ME LEAVE!
Oh, boy, you don't want to know what it took to finally get me out of there. And by that point it was too late. I share joint custody with him now. Whoopee.
Where I went wrong? I trusted him way too much. I trusted that he would finally get sober. I never bothered to get proof of him using. I took him to court and he denied everything and painted me as an unstable villain. Even brought up my high school suicide attempt from 18 years ago, as well as drug use from before my kids were born. I didn't deny a thing. Guess I should have. Seemed to work for him.
Anyway, go ahead and hold out hope. Maybe he'll turn his life around. But do not let that stop you from gathering evidence! Gather evidence! If he's willing to submit to drug tests, he should be willing to do them at an actual facility, where they'll be valid in court. Witness collected. Otherwise he's not really serious about his recovery and you shouldn't give him another chance. Hope for the best, prepare for the worst.
You would not believe what my kids tell me about their visits. They are in danger. But will it ever qualify as "immediate danger"- enough for the courts to finally get involved and freaking listen to me? Who knows.
Don't be like me.