Missed period

Ok so a week ago was the last time I saw my boyfriend and we had intercourse but it was just a couple thrusts, kinda like a tease because we didn't bring protection. I'm 5 days over due on my period but I know he didn't ejaculate in me. I know I should be more careful but we were careful. I tried doing a urine test(without a pregnancy test) where if you pee in a cup and leave it for 3 hours and it stays clear then your not pregnant. But if it gets foamy at the top your pregnant. There was no foam at the top and it remained clear. I've done research on precum and it has no sperm in it. I don't know if I'm pregnant a or if my cycle just changed because summer started and I began to be more lazy. Someone please help.