Thanks, everybody, for your advice.
Last night, I went to NM's child support enforcement bureau website and filed for services. They'll look at all the financial data and determine an appropriate amount (the $ amount hasn't changed in 8 years) and set everything up so his wages are garnished and they'll send a check directly to me. I dragged my feet on this for several years, but I guess I finally just got mad and frustrated enough to do it. I thought it would piss him off, and when I told him tonight what I did, he was angry, but better him than me for a change!
I feel OK about it. I just feel like he and I shouldn't talk about money. It's not good for anyone. It's not good for the kids to see him giving me money (He ALWAYS manages to give it to me in front of the kids.), and I hate hate hate asking for it every time. This, at least, will remove all of that tension between us.
My DH is so proud of me for doing this!
He's been great about not pushing me, but I know this is what he's wanted me to do for a long time.
I just have to say it: this is a miserable way to parent. I hate it for all of us. I have a very hard time getting past the guilt I feel for having children with a man who was so very wrong for me. Of course, my kids wouldn't be the same people they are if they didn't have the parents they do, so I can't exactly regret it. I guess it's the fact that I love those two kids right down to my bones that makes it so awful. It's just so hard and so painful sometimes and it really scares me.
Eventually, I guess I'll have to face my real fear, which has nothing to do with money. Whether my ex ever gives me another dime, my kids won't go hungry. I'm not too proud to go to the food pantry and get a box from them. It's their safety. He just doesn't worry. My daughter almost drowned two weeks ago because ex let the kids play in a fast-running river and she got caught in the current. A stranger pulled her out, and ex wasn't anywhere around. On the same trip, he let them drive ATVs (they're 9 and 11!), without helmets, no less! These are only the most recent incidences; there have been many others and it's been getting worse as they get older. This nagging fear has been kicking my butt since they were born and it's not going to go away any time soon. I've discussed all this with a family lawyer, and there's nothing I can do.