PREGNANT OR NO? Neg tests but wacked period and symptoms?

Okay, my last period that was regular in time and flow was january 16-21st. After that my periods started to come within 10 days of when my normal periods would've came. My periods since january have only been 4-5 days of brown/red/pink spotting. That would come in place of my period (timing of now irregular "period" mentioned above). I was VERY tired for close to 2 1/2 months now all of a sudden I feel very awake. It happened overnight. I had a few days of nausea and lower back pain a little less than month ago. I never threw up though. I never get headaches but had a headache almost everyday over the past 2 months, they're finally going away *thank goodness*. I've had bad heartburn over the past month or so, which I never get, over almost anything I eat. I can take a drink of a coke and get heartburn for 5-10 minutes or even get it on an empty stomach. I had a sharp pinching feeling in my lower abdomen that lasted about 15-30 seconds one night after a few days of dull pulling/pinching pains ***** I just felt a flutter/pulsing feeling about 3 inches below my bellybutton, I've had this feeling before but now (compaired to the last week and a half when they first started) they're now getting stronger ***** I've taken multiple pregnancy tests, different brands, different days, different months, etc. I took one this morning that was negative but with all this stuff that's out of the normal with me and a wacky "period" makes me uneasy about not being prego. I'm not ttc, I just need to know what to think about this. I was pretty moody a few weeks back but I've had a temper problem in the past (my mom thought I was either bi-polar or depressed) so I've learned how to control everything on my own so I don't think much of it now. My ovaries felt achey for 3-5 days, like they were swollen or bruised, but today they feel fine. Idk what's going on, if someone out there can help me please post an answer!!! I'm 19, single, and lost on this.