While there is a genetic predisposition to getting MS if someone else in the family has it, or some other autoimmune disease (like lupus, rheumatoid arthritis, or a host of others)
there is no definite genetic link. Unfortunately, the fact that no one else in your family has MS means little. It could be that you could get it, or something else.
Depression and other related illness DO "run in families", so with a history of that in your family, it would be usual for the doctor to focus on that, and perhaps miss what is going wrong with you.
Have you only seen a neurologist? If so, you might consider seeing a rheumatologist, as what is happening might not be neurological in nature, but something like a chronic infection internally, that is causing your symptoms, or one of the other autoimmune diseases, like lupus. A rheumatologist would be more attuned to discovering that.
But you also need to understand that it can take a LONG time for symtoms to develop for many of these related diseases...enough symptoms to develop for the doctor to be able to determine what is wrong.
The fact that you've had so many tests come back negative only means that -- as of now, there isn't enough happening that will affect those results, and if the doctor can't see concrete evidence of disease, then he is left with "emotional problems". That's tough, but it unfortunately is pretty common.
One thing you can be doing is keeping a log of any new symptoms, or when "old" symptoms re-occur. Note things going on around you -- seasonal differences, or temperature/humidity differences, or other things like that. You may find some pattern there (like, some allergies can cause weird things on your skin) that can help the doctor focus his attention on something other than "emotional problems".
I'll go back through the posts here and see if I can find the one I posted about "signs and symptoms of MS", and bump it to the first page. Look for that, and see if indeed any of the things you're experiencing match anything in that post. Getting the right language to describe your symptoms might be helpful when you next see your doctor.