I had a baby 4 weeks ago. i had sex 2 weeks postpartum, i tested today and got a positive test. could this be left over hormones or new pregnancy?

Probably ”leftover”: A “new pregnancy” is really quite unlikely. Your positive pregnancy test is most probably due to “left over hormones”. Be safe. Repeat the test, preferably a blood betaHCG one, in another 2 to 3 weeks and postpone another pregnancy by 2 to 3 years by asking your gynecologist for the most effective contraceptives which are the intrauterine device (IUD) or the subdermal implant...plus condoms.