Question: could I be?

My last period was april 10th. I have a 4 1/2 year old son who i was only able to breast feed for 6 weeks. After my milk dried up i have not leaked anything since. I noticed the other day when doing a self breast exam that i had a very dark vein going down my left breast when i moved my nipple around some colostrum came out. My breasts have also been extremely sore and i have been unusually tired. Could i be prego? Can you leak that soon in pregnancy? My periods have been pretty regular every month. The last couple of days i have noticed that i have had to urinate more often also..