Unless your doctor advises you not to have sex then you should be able to as long as it isn't rough sex. My midwife actually told me that sex will help calm a baby down if he/she is really active. The rush of endrophines we get after sex also goes to the baby and causes the baby to relax and go to sleep. Let me tell you it works. So if you feel like having sex, then you can enjoy yourself. Though if you are this worried (which is completely understandable), I would speak with your doctor to have a medical opinion.
xox