Hi and welcome,
Congratulations on your new bub, I'm sorry your body is making the situation more difficult than having a new baby already is.
It's highly unlikely what your experiencing is being caused by a neurological condition like MS though, the crawling under your skin sensation spread 'all over your body' which is not something MS lesion damage can do. You've also experienced a very rapid development over a very short time frame of many different types of symptoms, it's not only bilateral but in all peripheral limbs.
You've also developed boils which are not a symptom of MS but a localised deep skin infection that starts in a hair follicle or oil gland usually caused by a bacteria called Staphylococcus (staph) and possibly from scratching with the itchy sensation, try not to scratch if you can try applying ice to distract and alter the sensation long enough to help stop the urge to scratch..
What you've been experiencing is not how a neurological condition like MS typically first presents, a symptoms pattern that spreads, all over, all peripheral limbs, rapid development of different types of symptoms, short time frame of weeks to months etc are all red flags pointing away from neurological conditions like MS!
I can only suggest you consider looking into all the strange sensations and other things that are associated with postpartum in the baby forums you'll find here and else where on the net...
I hope that helps.....JJ