Am I going crazy or is something really the matter?!?

Okie soooo my time of the month is late by a week. I've chalked it up to me working 20 days straight back in april. at some point last week, i started getting nauseous when I ate food (possible gall bladder problem?). It still happens. I read about early pregnancy symptoms and what not...aint gon lie...i have some of them but not all. Also, when i lay on my stomach, i feel pressure below my belly on. I took a hpt yesterday and the control line never came up and took one this morning and it was neg. What the heck is going on with me? I can't go to a doctor (just had dental work done so ran out of money haha paid out of pocket). I highly doubt you can get pregnant when its your first time and the condom slipped off....can you? ugh! as you can tell im a lil freaked out about it but since the test was negative i have nothing to worry about....right? or could it really be a gall bladder problem since ive recently lost weight (wooo)? any advice? dont know if this has anything to do with it but im 21.