Why are my nipples sore and breast isn't?

I had unprotected sex the day after my period ended which was feb. 17 and unprotected mar. 7 i've take 4 hpt and all came out to be negative i've been having discharge like crazy and from the look of it i even have a lina agra from my navel to my pubic bone...im a big girl and i've always had stomach but it looks like it has gotten bigger and harder. my breast are not sore just my nipples.could i still be pregnant even though i've had 4 neg. hpt