Period starting and stoping, is that normal? Could i be preg

Can you get pregnet if the guy never cums? from pre cum or whatever it is called . from him.. Because i had sex and the condom broke but her never came an after it broke . we just stoped cuz we were kinnda scared.. and then 2 days later i think i had my period, but it was only for 2 days but it was stronge. and then it stoped and the next day i thought it started again because i saw a spot of blood on my underwear but when i went to check it there was nothing... And last mounth i had sex for the first time, two differnt times and the first time i had my period like 2 days after again but it started befor i had sex and then it stoped for a day . and that is when i had sex and the next day i was bleeding again. but when i had sex i did not bleed so i don;t think its from that. Is it normal for your period to be at a different time every month, like mine has always been. and then to have it start and stop.