Am i pregnat?

I am 18 I havent had my period for 6 weeks! ive been having bowl movements 4-5 times a day my chest is heavy and perky and i can feel heavy like sacks in each chest like i had implants or something! my stomach gets really big when i eat and im havin pains in my lower right area of my stomach and latly ive been gettin shooting pains threw my left arm! i walked about half a mile to the store today n then back got a pregancy test and drank a whole botle of wart while doing it when i got home i tock the test it said negative n then later i started my period ! but why am i feeling all these ways i dont understand! PLEASE HELP!!!