Did they do any other testing, like STD testing? (I'm not implying anything about you, and have no idea what your risks may or may not be.)
Did they find any blood in your urine?
Sometimes, foods can irritate the bladder. I'm guessing, as a mom of an infant, you aren't eating the best, so make sure to be drinking lots of water, avoid caffeine, alcohol, fruits (the acid irritates the bladder) - and here's a long list of possibilities:
I'm assuming your obgyn did an exam, and everything is fine from the c-section?
I'm sure it's scary, but if altering your diet doesn't help (or you don't need to), then a urologist may really help.