You could be in menopause.  For sure you are perimenopausal.  It's possible that your periods have not resumed because of being on Depo Provera for so long.  The best way to check is ask your provider to draw a FSH blood test (follicle stimulating hormone).  With no periods for so long, you won't have another way to tell.  Breast tenderness is very common when your hormones are out of balance, especially if your progesterone is low.  It's the same as when women have sore breasts before a period.  The progesterone drops to bring on the bleed and a number of symptoms can come, including very tender breasts.  I'd recommend you check in with your provider so you can inform yourself and know what is going on and what to expect.

Sandy