This Is A Long Story. I Am A Female And

This is a long story. I am a female and about 1 week ago I lost my virginity. But we didn't use a condom. It didn't last long at all, in fact there was a lot of struggle. The guy didn't cum in me though, I'm just afraid he might've got precum in me. I did notice before/afterwards he was having precum. But also that night I smoked and drank alcohol. I also ate a strange microwaved biscuit around the time I drank the alcohol. The only things that have been going on with me currently is diahhrea/constipation. It's a yellowy liquid. I'm concerned that I may or may not be pregnant, or is it just the alcohol and strange foods I ate. To get an idea, I ate a biscuit, onion chips, steak, and pizza. My boobs aren't sore at all, and I haven't witnessed any for sure signs for pregnancy. But I am very concerned. (Also keep in mind I am not on a pill either..) My period is supposed to come within the next few days, so I will see if I miss it or not. Do you think I'm pregnant, or could I have IBS? Or could it just be the combination of foods and alcohol and smoke? Also, I have lost my appetite recently. I really need help, thank you.