BirthFree - I've been having the same problems as you. I too have an "irritable" uterus. That was discovered with preg #1. It didn't get any better with subsequent ones, and now on #4, seems to be worse.
Last week I had 3 days of very worrisome BH. Each day they would start in the late afternoon and last the rest of the day. Nothing I did helped. They were strong (uncomfortable, not painful), but that's how they always feel. I just hadn't ever gotten them so close together. Instead of every 10-15 minutes at the most, they were coming at least every 5 minutes. I decided I should take it easy for a few days (I had been extremely busy with work and school and other crap) and by day 4 things started calming down. It's happened a couple days since then, and it seems to be after I've been on my feet a lot during the day. I decided to quit work (I was working as a nursing assistant) and as of Tues I'm done with school, so I'm expecting a big improvement. I think it was my body's way of telling me to chill out.
Anyway, that was my long winded way of telling you that I know exactly what you're dealing with. It's kinda scary. I'm afraid that trusting my body will cross the line into denial and I won't recognize if it *has* turned into preterm labor. That kinda freaks me out.
I'm betting we'll both carry to term just fine. I just hope our uteruses aren't completely pooped out by the time labor really starts!