Hard Stomach, Uncomfortable feeling. Contraction? Cramps?

Currently in my 21 weeks, and I've been having this "hard stomach" with cramps/contraction quite frequently now every few days even when I'm asleep. Is it normal? I know that that in 2nd trimester you will experience it, but I'm not sure how frequent it is. Please share your experience / thoughts #firstbaby #1stimemom #pregnancy #advicepls #pleasehelp