Myasthenia Gravis AND MS??

Been to see Opthalmologist and Optometrist today as been having intermittent double vision, drooping eyelid and nystagmus. Assumed it must be MS related but consultant concerned that symptoms fit with Myasthenia Gravis so sent me for further bloods and referred me back to Neurologist asking him to check for MG. What are the flipping chances of a SECOND condition of auto-immune origin - or does my body just hate itself so badly that it wants to attack itself?!? I am really not sure what to think - I know that having one long term health condition does not exclude me from getting another, did google both conditions together and then came up with a few hits where MS and MG were associated. Am probably just thinking too much but has anyone else heard of MG in MS patients???