I had sex in the middle of my cycle, unprotected, no birth control, only entered me twice, did not ejaculate. I got a pimple on my vagina a week after that. I had become terrified of pregnancy and began stressing a lot. My period came 5 days late on the first Thursday of the month.I took a pregnancy test a day before my period came and it was negative. My period is usually 26 days apart, I never really paid attention. My partner and I had done the same thing this month but he only went in once and then it went no farther then that. My period came again on the first Thursday of the next month. So exactly 28 days after my last one. My periods had changed. Both only lasted about 5-6 days with heavy bleeding, but I had extreme cramps with my first period. The next one seemed to be the same as the last one but without the. Extremely painful cramps. I have no appetite for the last month really and my bowel movements are just little but I have a lot of them. My urine is dark and my stomach has a weird feeling when I urinate or when I have a bowel movement. I expect my period tomorrow, should I be worried about pregnancy?

The pimple could be a sign of an infection or a STD

He only needs to be in once, if there is any fluid what so ever ( the early fluid) that is all it takes.

How old are you ? Periods change, come shorter, longer, more or less painful, And worry and stress can even make you miss a period.

Also you can not do a pregnancy test before a missed period, you can do it about 10 to 14 days after you miss the period.