I always got noted as having dense breasts pre-menopause. The last mammo I got, last year, I was finally menopausal, and the attendant asked me if I had lost a lot of weight. Uh, no...just gone through menopause -- they have definitely shrunk! I can feel that my 53-year old breasts are much softer and less dense. It's a blessing in some ways since a lump would be much easier to find. Pre-menopause, they always felt lumpy and bumpy.

In other words, you're perfectly normal, IMO.