Did you go through any counseling after your experience? If you didn't, then you might want to try.
As far as the physical situation, I guess what I'd ask is first, are you sure that there's been adequate foreplay before you attempt intercourse? Do you feel completely ready until the moment you try? If you're not, then continuing to try is only going to make things worse.
Can anything at all be inserted? Are you able to use tampons for instance? Can you use something like a sex toy when you're alone? Or does this problem happen always no matter what?
If this is always a problem, then it sounds like your first step should be talking to a doctor who specializes in problems like vaginismus.