Can I get on a rollacoster while my first weeks of pregrancy?  

I would not. Although, rollercoaster rides are not contraindicated in pregnancy, but if that is associated with scary feelings, I would not go for it. Remember, it is not just you but also your baby is going to feel what you will. Why stress him? If something goes wrong with your pregnancy, chances are you will be blaming it on the rollercoaster. Better safe than sorry!