I have both MS and GERD (reflux). I've had IBS off and on over the years.
I've had most of the symptoms you described at one point or another with the exception of MS hug.
It sounds like it could possibly be MS but like you said, your pre-existing digestive issues could be clouding something else? (That's the way I read it anyway.

)
If it's a bonafide MS clinic they should be able to either diagnose or rule out MS, eventually. Sometimes it can take awhile though so be prepared for lots of tests and some waiting and seeing. A small percentage of people are diagnosed quickly but it isn't ususally the case since MS can mimic so many other illnesses.
Take care and keep us posted on whatever you find out.