What's wrong with me?

i've been on Depo since my baby was born in 2004, it is now 2007, i dont ever see my period, but my breast has been hurting for 2 weeks straight really bad, i still have colostrum in them, still, i've been having severe cramps for 3 days straight so far, they feel like contractions and my lower back aches each time i feel them, i took a home pregnancy test, and it was negative, i need help