Yellow discharge and l pain during pregnancy...?

I'm 23 weeks pregnant and for the last two weeks I have been experiencing pain in my . I know this sounds weird...It's not itching really...but like a constant burning and every few minutes a sharp pain shoots through it. I went to see my ob and instead of checking it out, he just told me it was yeast and to use over the counter monistat. I did and it hasn't gotten better...in fact, it's more painfull and the discharge is now clumpy and yellow....like greenish yellow. So I'm going in to see a different doc tomorrow..I am just curious if anyone knows what this is...and no..I don't have an std....