Could I be pregnant?! please help!?

Alright so. I had protected sex [condom] around the end of March, right after my period [Normal or Heavy flow]. Then on April 25th I got a very light period, which was mainly just spotting. Then I had protected sex right after that period twice. I thought everything was normal until 2 weeks later I got another very light period, also just spotting like the last one. I haven't had sex since. But I haven't had my period since either. Also, for the past few days my breasts have been sore, [and possibly bigger, but that may just be me being paranoid] and I had a little bit of diarrhea this morning. Also, about a week ago I had clear/whitey discharge and I have that a little whenever I pee now [just a tiny bit]. But here's the thing, I took a pregnancy text 2 weeks ago and it turned out negative. So, do you think I could be pregnant? Or is this just a change in my menstrual cycle? [Also, I've been under stress for the past few weeks and I know that can effect menstrual cycles]