Hi and welcome to the group.
I don't think that naltrexone in such a low dose could do any harm. I have heard of some people that had some complications with LDN, but in general it is safe.
If you have MS, starting LDN so early is the best you can do. You will avoid any neurological damage. On the other hand, it is quite possible not to experience any more MS activity while on LDN, so you will never know whether you have MS or not.
If I were you, I would start LDM immediately, without second thought. And do not stop it if you feel that you are healthy. You MAY have MS.
If God created MS, Devil would create Rebif to treat it!