Sorry to hear what you are going through. Hopefully your doctors are working hard and will be able to give you some answers soon. If you believe that there is something going on physically and is not caused by anxiety you will have to be firm with the doctors. It is possible that the anxiety is being caused by you having physical issues while trying to care for your baby.
An MRI should be helpful in indicating or ruling out MS. You should try to get a brain and spine MRI, because sometimes lesions will not show up on the brain, but do show up on the spinal cord.
Your symptoms are kind of vague and could probably have any number of causes, so you may have to hang in there for a while until the doctors can sort things out. Try to find someone to help out with your baby in the meantime-a family member, a friend, maybe someone from church?