possible pregnancy ??

okkay so this is my story .. I BELIEVE IM PREGNANT AND IN THREAT!!1

I have always been irregular in my periods after the age of 16 my period came on the exact day..so to make it short in November after thanksgiving i received my period , it stopped the first 2 weeks of december i was being really sexually active. and in the 3rd week i started bleeding (spotting) with cramps after that i started with heavy bleeding and now is non stop i been bleeding all the way ive taken a HPT and one came back negative a week after took a 2nd one and came back 1/2 postive line was faded && i did a blood test but still negative. ALL my aunts including mother have found out they are pregnant through ultrasounds because it always come back negative in urine or blood :) .. also my pants dont really close no more when i stress out i feel a big pain on my lower left abdomen and when im standing up to much my feet get swollen. been having some back pains too and i look at my self and it seems i gain weight but my fat is not going to the sides i feel is going from up and out .. what do u think