I think that worry in the early stages is pretty normal. It is all such a new experience and you really dont know what to expect from any aspect of it. I took the mantra "Don't worry about the things you can't control". Excess stress causes increased cortisol levels ( a hormone) which isn't great for the baby. You just have to keep going on with life as best you can whilst feeling terrible from ms and tiredness and take some reassurance from that. If you really want some extra reassurance you could always have an early ultrasound.
If there is any time to listen to your body it is now. if your body is telling you to eat - then eat, telling you to rest - then rest.