Milk supply

I normally pump and give my son a bottle. I do give him my breasts a couple times a day, but I generally give him a bottle because I know he eats more that way and isn't up crying because he is hungry every 10 minutes. Well today I've only given him my breasts because I haven't been able to pump. He sleeps for 10-30 minutes and is up and hungry again. I've noticed that every time I have fed him today my breasts would tingle and the one he wasn't on would leak. And I mean every. Single. Time. Is this my milk production increasing? Or is it just because my body knows I'm feeding him?