Feeling Baby?

I'm hearing everyone talk about how they can feel their baby move, I will be 18w tomorrow and I don't feel a thing. 
I've read that it feels like flutters or gas but the only thing I have felt is a little pressure every now and then in different spots, but I don't know if that is the baby moving or just ligament pain.  
This is my first pregnancy so I have no idea what to look for. What did the first movements you felt feel like?