How does contraction feel like ?

Tania
This might sound silly but I'm 35+4 and I feel huge ! I don't think I'm gonna make it all the way to 40 weeks ! Sometimes I feel like pain on the lower part and I've been told it could be HB ! But since it's my first I don't know what I should feel ? How doest feel to have a contraction ? What are the signs that the baby is coming ?