Itching!!

I have recently started being sexually active after months of not, and everytime a day or two after intercourse I would itch like crazy for a few days and then I would have trouble peeing, just like a burning feel. I finally went to my gynecologist and they tested me for stds, yeast infection and one more but they all came back negative and with my physical exam she said she definitely saw some sort of infection, a week later and I am still itching and a feeling I have to pee, any other ideas of what it could be?? I have tried uti pills and anti itch cream and nothing works!