Sore nipples?How early can you tell?

In march I had a missed miscarriage and a D&C done on 3/11/11. Then I had a cycle on may 4 and another on june 4. My cycles used to be irregular but late last year started averaging about 31 days. Since this last cycle was 31 days long I'm assuming this one will be too which puts my next period at 7/5/11. I've been having sore nipples now for a couple days. No, this does not happen ever. The only other time I had sore nipples was mid February(the month I concieved-AF was on the 5th i think) before I found out I was pregnant. Then It got really extreme right after I found out which was about 3 weeks later. Anyways, does anyone have any reason why they might be sore? is it too early for a pregnancy symptom? My period is due in 8 days i think.