What does the baby kicking feel like?

I'm 20 weeks pregnant today. We went for our sonogram last week and the baby (a boy) was moving the whole time... even kicking my bladder, but I haven't felt anything different. I have been (sorry if this is TMI) really gy for most of the pregnancy. I don't know if it's just hard for me to tell the difference between the gas and kicks. What does it feel like? I'm imagining it would feel like someone inside is kicking you! lol