Cramping second trimester

Hi. Need your help. Woke up last night with a astring cramping pain in my low abdomen. It lasted just a couple of minutes and I felt asleep. Now I feel just like mild cramp pain. No bleeding at all. My concern is that I was already feeling the baby move and I haven felt anything since last night before de cramps. Should I be concern? I have read is normal but I can't calm down. Any of you experiencing the same? I am 18 weeks 1st baby. Thank you