Embarrassing sex-related question...

I’m almost 20 weeks pregnant and figuring out how sex in a pregnant body works...quite an adventure so far 🙄

We were fooling around this morning and my husband was sucking on my breasts (nothing new for us) and when we were all done he just goes “hey, when I suck on your nipples something comes out...is that milk?” We are very open with each other, but it caught me totally off guard. I think my face turned bright red and I immediately started googling for answers...is it really possible for that to happen this early??? Will that happen all the time now? Im not embarrassed about it happening as much as I’m embarrassed that I don’t know much about it...