Be honest and let him know- 1 of 2 things will happen:

He will:
A) not be able to handle it and leave which would really just save you time more heartache, because anyone you are with has to be in it for the long haul.

or

B) accept you for you, take all your good qualities plus the crappy MG with it and accept that although you have MG it does not define who you are. If he does this you guys can plan dates that won't make you so tired- i.e. dinner OR a movie, but not both in the same night.


Hope this helps!