I just went up to 1500 mg a day, and am looking into my vitamin D intake too, to be sure I'm getting the benefit of the calcium. I had only been taking 500 mg when I thought of it, plus a couple of hundred in the prenatals I take (due to nursing). Yes, a strong history -- two grandmas bent over by the time they were in their 70s. :( It's a good thing my main medical provider, who is a nurse practitioner, was keeping her eye on things like that, because my high-risk ob-gyn never once thought of it.
My personal feeling is that if you have a strong family history of osteoporosis, you should be on calcium supplementation. Breastfeeding, pregnancy, or not.
Gosh, my mamacita suffers big time from that! I hadn't even thought of that - good thing to ask your (or my) doc.