I'm 32 and I have been on the Depo shot for about a year now. My last shot was April 5th and I was due for my shot between June 25th-July 5th... I was about 2 weeks late on it though. But about the 2nd week my breasts started to hurt... just the side of my breasts and they usually only hurt when I wake up and cease during the day. And they didn't hurt everyday. The pain wasn't horrible just more sore. I know it could be because of pregnancy me and my boyfriend had unprotected sex with the pull out... but this is the only symptom I have and they aren't a different color, my nipples don't hurt, I haven't seen huge growth just sore when I stand up. And I also read that the depo shot could cause this. I got my shot the 29th and my breasts haven't hurt for about 3-4 days except today now. So I'm just wondering all the possibilities of why they could be sore. ALSO I BEEN WEARING A VICTORIAS SECRET PUSHUP BRA AND ONE DAY I Didn't WEAR IT MY BREASTS Didn't HURT THAT DAY. But I just need more insight on this

Someone?

Sometimes breasts will just ache for no apparent reason. Could be simply hormone changes. Since your last shot was late, that increases the possibility of pregnancy. Are you still having periods or have they stopped while being on depo? If you still have them, are you due soon for one?
Maybe it is from the injection as you mentioned, even if you have not felt it before.
I assume the push up bra has an underwire? This may have been causing some pressure and causing some discomfort.
As you can see, there are a number of possible reasons for breast soreness.
If you think you could be pregnant, try a pregnancy test. If they continue to be sore, and you can't determine a reason, check with your doctor.