brown discharge, sore breasts and nausea

Am i pregnant?

Me and my bf had intercourse and used the pull-out method in mid November. I haven't had my period since. I took a pregnancy test in December and it came back negative, though i did not take it in the morning. I figured if i was already pregnant, then even if i drank a lot and took the test the results would be accurate. Anyways, I read up on how stress can cause missed periods, and i started thinking it was that since a lot has been going on in my life...then i started having brown vaginal discharge. It lasted a week to a week and a half. A couple times there was bright red blood in it. One night i had severe "cramps" in my lower back, i couldn't even get out of bed. Every now and then my sides are more sensitive than before, my breasts get a bit sore, and i feel nauseous. Once to twice a week i vomit just a bit (as small as a tablespoon)-most of the content being acidic . I haven't been eating properly, but then again i usually don't-my BMI is underweight...but since it's been that way i doubt that's a factor. My stomach seems to be getting bigger...i often feel bloated and bigger than i use to be. Am i pregnant? Please help me out. I've been on google non-stop adding on to symptoms. Thank you in advance for taking your time to respond.