Pregnant at 15??

Hey guys so I’ve been feeling weird for awhile now and every pregnancy test I took the was always a faint line but it could have been an evaporation line🤷🏼‍♀️. I’m only 15 so I don’t really know. My stomach is growing but if I am pregnant I would be about 22 weeks. Since I have always been very skinny I’m not really showing but I’m bigger then before pls give me any advice u have. :) also breakthrough bleeding for awhile(if pregnant)

P.S. I heard if I take a test again now at 22 weeks it’ll be negative anyways