Baby hasn't moved in two days?

I started being able to feel the baby kicking and even seeing my stomach move from the kicks at 16 weeks. I'm now almost 18 weeks and haven't felt baby move in two days. The past couple of weeks the kicks have been pretty regular if I lay down flat baby goes crazy so I have tried and tried to lay down flat so that baby will move but it hasn't I have been having Braxton hicks contractions for over a week but my mom didn't seem concerned I'm starting to get a little worried considering I went into preterm labor with my first child SEVERAL! Times. Should I go to the ER and get checked to ease my mind or just wait to see if baby moves?