Missed period, tender boobs, & after I pee, my vagna burns & feels like I stil need to pee but idont

I had unprotected sex toward the beginning of May. He pulled out before he came. I still haven't had my period. My last period began April 22. I had a lot of gas and cramps for just about 2 or 3 days and my boobs have been tender and sore. Those were the only pregnancy symptoms I have had though. Just in the past few days, my vagina has been burning and I always feel like I have to urinate, even though I don't have to. Right after I get done urinating, I still feel like I need to urinate more and it burns. I had a yeast infection a few months ago...I'm just worried that I could be pregnant.  Also, I took 3 pregnancy tests in the last week and they all came out negative..
Also, I had a late period in February...about 20 days late..thought i might be pregnant then but I wasnt.