Am i pregnant?

Hey. will im a 17 year old girl whos engaged and at the moment freaking out. Here is my story. About a year and a half ago i went onto the injection and then i stoped it about 6 months ago and went onto the pill i sometime (only lately) forget or take it late. I last had my period somewhere around the begining of december thats when it stopped. About 2 days ago i started bleeding again it is a light flow and the blood is brown. I took a pregnancy test about a week ago but it showed negative, i cannot affored a doctor so please dont say i should go to one. I have no pregnance symptoms other that the bleeding and i generally pee on hell of alot so i cant tell from that. I have hypoglocemia so its hard to tell as far as dizziness is concerned but i do get tiered alot lately. as far as i know the injection can stop you for falling pregnat for up to a year after you have stoped it. I buy a pregnancy test once a month just to be sure but it said negetive and now a week later im bleeding again. Is it possiable im pregnancy
the pregnancy test didnt pick it up because its so early in the pregnance. could it be because i havent been taking my pill same time everyday? its never happend to me before i mean the bleeding and i havnt been taking the pill as much as i should since november. am i pregnant? Please help.