I may be pregnant.. please help!!

This is a pretty confusing situation, and I don’t think I’m pregnant but I’m not sure. I’m hoping that some of you guys can help me out.

So my last period before I had sex was June 27- July 2nd.. on July 4-7 I had sex everyday for that weekend and an hour after sex on the 6th I took plan B. Then a couple of days later I was bleeding but not heavy kind of like spotting. I told my OBGYN and he said it was just side effects from the plan B. On july 11th I went to my doctor to start birth control. I didn’t actually start the birth control until July 12th. Once I took the birth control I didn’t have a period until August 7-August 11, my placebo week. When I got my period it wasn’t a red color it was black brown and a lot of clotting... now my boobs are super sore, I also kinda pee a lot but I do drink a lot of water because I’m always on my feet at work for about 7-9 hours everyday and sometimes I’ll get nausea but majority of the time I don’t. A coworker of mine who has had 5 kids said that it may just be the planB and birth control messing with my hormones.

I’ve tested 3 times: one time after I took plan B then twice on July 27 and all three tests read negative.

I’m not in the mental space to have a kid right now and neither is my boyfriend. Both is us are just finishing up college and starting our lives, both of our families would be super disappointed in us if I am pregnant . If any of you could help me I would really appreciate it.