little monkey movements

Lilly • 19 years old. married march 3, 2015💍💑miscarried twins may 8, 2015. 👶🏾👶🏾expecting baby #3 march 2016. 💞👶🏾
this is my second pregnancy, unfortunately for my first i miscarried my twins at 18 weeks. im now 17 weeks and have questions about my little monkey's movements. sometimes when im laying down, i feel a tightening in my stomach that lasts a couple seconds & then goes away. i was wondering if this could be me feeling my little monkey move or if its just my muscles tightening.