Hi and welcome!
I, too, am un-dx'ed. I have had clean MRI's on both my brain and cervical spine but, at my last appointment, my neuro made the comment "I'm concerned it's MS but it's just further down". I was so flabbergasted he said that (you'd have to know how super cautious my neuro is to understand that his even mentioning this without some evidence is really a big thing) that I didn't question him. I just sat there stunned. It was only after I left that it hit me "Did he just say that and I didn't question him????"
Our health pages are really GREAT sources of information. I would suggest you check those out. This one deals with negative MRI's:
http://www.medhelp.org/health_pages/Multiple-Sclerosis/How-Can-a-Person-with-MS-Have-a-Negative-MRI/show/161?cid=36
and there are many other ones as well that talk about lesions, etc.
I, too, am waiting on an appointment for an LP but LP can be negative with MS as well. They can also be positive on someone who doesn't have MS. LP's are just a tool and can't rule in or out MS definitively. This health page:
http://www.medhelp.org/health_pages/Multiple-Sclerosis/Can-you-Diagnose-MS-with-an-LP-that-is-Negative-for-O-bands/show/142?cid=36
is an EXCELLENT one on LP's.
I don't think anyone wants to have MS but I am a firm believer in the fact that "Knowledge is power" and the old adage of "To be forewarned is to have four arms" or something like that.... ;) (Just a little humor. Better to laugh than cry....)
Again, welcome. Take a deep breath. Do some reading and ask some questions. I just recently joined this group and the support is amazing here. Even and especially for those of us wandering in "Limboland" awaiting a dx....