pregnant or not wats implation bleeding during pregnancy hows it differnt from a!

im confused, i have a light period not as heavy as it was 2 yrs ago but in nov i had sex it was on the 24th got period dec3 got period dec 24th got period janu 22 took a test feb 11 it was a free clinic it was negative and then got period on the 23 of feb, took test march1 at health offcie with doctor and also neagtive took a home test 2 weeks after that also negative took them at 1pm 3pm and 5pm got my perios march 22 im stil on it but its light, all my periods lasted 5 days and were light/kind of heavy.light again is it spoting/implation bleedign that women get when they are pregnant or is it my normal periods just changing? am i pregnant or not with 3 negative test 4 normal periods on now will be my 5th because i had two periods in december???? no signs or sytoms i did gain 5pounds but thats because iv been stressed and eating cause my tummy isnt hard and its been 4months since havin sex am i pregnant? my step sister frekaed me out said i will end up like girls on tv and with no life??? please give me tips thanks in advance
so its been 4months since i had sex for the 1st time and iv had 4normal periods and im on 1 now i