Am I feeling movement??

Mary • Married 5/26/12. Police wife. Emergency room RN.
So the other night lying in bed I had my hand on my belly and my eyes closed and I could have swore I was feeling like a twitch or a ticking in my right lower belly. Last night I felt the same. The first night I had some tummy troubles and felt really constipated so I just thought it was gi related but last night I felt it too! Could this be early movement? Felt like a one second tick or twitch in my belly. I have an anterior placenta to the left (my right is open).. And I'm now 18w2d today. What do you ladies think?? I'm a first time mom and unsure!