I started to feel him around 17 weeks, but wasn't for sure if it was the baby or just gas lol. It was very light, and only once a day or once every few days. By the end of 20 weeks, I was for sure it was him. He must have had a growth spur because just within week 20 the movements got much stronger, and much more frequent. I'm 21 weeks now, and I feel him move all day long, and even feel him hitting my bladder.