Hi all :) really in need of some advise! 

I've been on the Depo injection for just over a month now but when I first had it done the nurse told me to wait a week so me and my partner did and after a week we had unprotected sex over the 26th-30th and since the end of last week I've been having very bad cramps in my lower stomach which has gone on all week, today when I got up this morning to do the school run I notice some pink/brown discharge/blood in my underwear (sorry TMI) and now I have no idea what to think! My boobs ache, every now and then I keep getting cramps and feeling sick etc! I've also token two pregnancy tests today and I think their both negative as can't see anything unless I shine my torch on them and then I can see something but not sure if my mind is playing tricks on me to be honest! I've also spoken to my doctor who is refusing to test me because he is saying it's all in my head and there's no way you could fall pregnant on the depo injection! Very very confused!

Please Help? 

P.s. Me and my partner won't be fussed either way but would be nice if I am pregnant :)