Help...

I’m 18 and just had my son 3 months ago, recently I just got my birth control needle sept 12th, 2018 and I have been bleeding for 7 days now... normally I bleed for 3-4 days then I’m finished but for some reason I’m cloting ( had one the size of a toonie and now the rest like drops of rain but in a clot..) and heavy bleeding... they didn’t do a pregnancy test before giving the needle... lately since I’ve gotten the needle I’ve had headaches and stomach aches... no cramping tho...