Yasmin and urinalysis

I've been on and off of Yasmin for about a year now. It seems like every time I am on it and I have sex I develop irritation. I went to my OBGYN because I was scared out of my mind. I took every STD test you could think of and he finally told me it looked like I was having rough sex. I told him that my sex has not changed at all. I did an experiment and got off of it for a few months and didn't have any problems down there while I was off of it...but as soon as I got back on it I develop irritation after having sex. I also notice that my urine smells very different and I am thirsty all the time. I can never get enough water. I thought maybe this pill was causing me to have UTI's. Has anyone else had these problems?