mmr83,
I am 24 weeks and having this problem. I think you should get checked, to rule out the possibility that something serious is happening right now. I ended up in the hospital for overnight observation 2 weeks ago due to this, and until they got the monitors on me showing frequent contractions, I heard similarly dismissive attitudes from everyone--there are other more minor things that can cause pains at this stage, so I think everyone kind of first jumps to the more obvious ideas, like round ligament pain, braxton-hicks, etc. I've been on modified bed rest since my hospital visit and have been holding relatively steady, have a follow-up tomorrow. They still aren't willing to do much unless the situation looks more serious, and I am terrified, but I feel a lot better knowing that there is somewhere to turn for help and monitoring, and that they have a record of my situation to refer to if I need help later on.
This is an awful situation to be in -- the next three months are going to feel like three years!.....I totally understand how much this messes with your thoughts and feelings, can't imagine how much more of a wreck I'm going to turn into over time because I already feel pretty crazy from this!
Please go get checked out, and good luck!
PS thanks to everyone else who has posted about this, even if it was awhile ago now. It's really helpful to know others have been through it too.