6 months not BF (TMI)

But last night my husband and I were .. you know .. doing the dirty. And he was playing with my nipples and that sort of thing. He said I started lactating. How is this possible? I breast fed for 7 months and my baby is 13 months now. I'm just shocked. I wonder if I started pumping all the time if I'd get a good amount of milk.. idk.