Ok I Started My Period Dec 13 And Had Sex

Ok I started my period Dec 13 and had sex on the same day.my period was very light and lasted for 3 days.normally my period is very heavy and lasts 6 or 7 days.after that I became very tired,very hungry,urinating frequently,and my breast became very tender.i took 4 pregnancy test and all came out positive.i bought 2 from the family dollar store,one from 1.00 store,and a Walgreens first step pregnancy test.so is I'm pregnant or not?