Nipples Leaking "Colostrum"..?

I was bending down and noticed my shirt felt wet. Lifted up my top and my left nipple was leaking colostrum. 
I am on CD 13; last AF was a day early. I have a 5 year old son that i BF for 2 mos; had headaches all week but I thought it was this detox cleanse we have been doing. Have had the usual symptoms but glow had my O day as today ...? 
Anyone else who has been pregnant before experience leaking YEARS later?