can I be pregnant?! please help urgent!!

we used protection every time and taking extra precautions and checking for little holes after. even though using a condom he didn't cum. I know you can get pregnant from pre cum but I know for a fact that in this occasion none had gotten in. we did however have direct penis and vagina contact for about 5 seconds although he didn't even have pre eiaculation when we did and it didn't go in. since, I have gotten a normal, heavy period and it was exactly like usual but I read that you can still have periods while pregnant. I have been stressing myself out since Saturday and it has made me feel quite sick which has resulted in me stressing more thinking about it being a symptom. I also have an upset stomach from the stress and anxiety. 

I took a pregnancy test on Sunday and it came out negative (took it at night but it was an all day any time pregnancy test) but I still can't help but stress. I don't feel as sick as of now but do you think I have any chance of being pregnant? I'm 15 and yes I stress a lot but I have only recently become sexually active. please help!!!