Am i pregnant or not. ?

okay the last time i had sex was in march. i got a normal period in april, and a weird one in march. VERY LIGHT !. I have not gottan my period in the month of june. a lot of this time i have been incarcerated. so I dont know if it is the sress or not. I took a prego test in jail and it was negative. I took an equate one from walmart and it came out negative, then i took two first response tests and they both came out negative. so i dont know what is going on. Is it possible that I could still be prego after all thse negative replies. or am i late. or what do you think. ??