What Causes Delayed Periods With Cramping And Back Pain?

hi, my last period was last january 10. and now i still don't have it. i have symptoms that i am not sure if pms or pregnancy symptoms. i think i urinate frequently, i have cramps similar to menstruation cramps, i have faster heartbeat, headache, my lower back hurts, i am bloated, and i feel uncomfortable in my abdomen more like i have too much acid. i had pregnancy test at home last night and it was negative.

i haven't been vomiting and do not have unusual cravings though.

i am really confused, i thought my period might be delayed because ive been worrying too much. please answer.. thanks a lot.