Pregnancy and Miscarriage?

Me and my partner had , few days after i finish my period(April 15-20). We used protection that 1st time but the 2nd time during the day, he didn't use a condom. My period is usually unregular, my last period had been april 15-21. I still didnt get my period and it was may so i tought since my last pd came earlie this one should too. but it on the day it's usually to come(24th), 3 days later only redish brownish spot would come out and lasted for 2-3 days like if my pd had ended.I felt tired, my felt sensitive, no morning sickness or anything though. June came and just recently i had been smoking and drinking. On the 16 of june that night i had smoked and drank, and i was feeling a lil crampish and back pain. The next morning i couldnt really get up and i went to the bathroom and it was just my period but that only last for 2-3 days because it came on sunday morning and now it's stoping tuesday the 19th. I had took 2 pregnacy test but they both came negative from the pharmacy. Whats going on?