My girlfriend has been on depo provera for the past 6 months. Her period doesn't come anymore, but she does spot some months. She also gets bloated for about 2 weeks.

For the past 2.5-3 weeks, she mentioned her boobs are starting to hurt and are very sore. She's had a kid before, and says her boobs hurt now like they did when she was pregnant before.

She took a pregnancy test around 9pm last night, and again this morning first thing when she woke up. Both were negative.

People have sore boobs when coming OFF depo, but I didn't think it happened when you were still on it.

Any ideas here?

Your girlfriend probably isn't pregnant, but I can't say for sure. Have you done any research to see if sore breasts are common when on depo provera? She could always ask her doctor about it as well. I've never been on depo, so I can't say anything from experience. Breasts can become sore for several reasons. There is a slight chance she could be pregnant and the test just isn't detecting it. Sometimes women can feel symptoms (such as breast tenderness) before a test can even detect pregnancy.
Maybe someone with more experience with depo can give you more info. If the soreness doesn't go away and she is concerned, she should probably just speak to her doctor.

Once her insurance kicks in again she will go to her dr. I've heard preg tests causing false positives, but seldom a false negative. Even if she is pregnant, I thought that depo provera can actually hurt the baby so I'm a little worried here.

Hopefully someone more familiar with depo provera can chime in here or point me over to the right spot to ask.

I was on the IUD and BC and my boobs NEVER hurt, well last month they hurt for like 1-2 weeks. It meant I was getting my period. It's probably hormones.

actually you have that backwards...false negatives are common but false positives are rare...if she is indeed pregnant she may not be far enough along for a test to detect pregnancy. I personally dont think she is pregnant if she is on depo provera but stranger things have happened

Sore breasts can be cause by alot of factors. Has anything new or stressful taken place in her life?
I'd wait a little bit & take another HPT and if you still feel uneasy go get a blood test or a EPT at your doctors to local clinic. Good luck honey! (:

I totally agree. I would sometimes get sore boobs before my period, but sometimes not. I've heard of Depo doing wacky things to hormones, so I'd put my money on that.