Pyridostigmine is a great laxative. We've all shared your issues. You'll need to take a regular anti-diarrheal or you could damage the plumbing. (smile). Leg cramps are a common side effect. But if they are severe, they could indicate a problem with acetylcholine toxicity. Pyridostigmine works by inhibiting an enzyme that breaks down unneeded acetylcholine. If acetylcholine subsequently becomes excessive, screaming leg cramps can result. Talk to your doctor about switching to an extended (slow-release) tablet or splitting your 60mg pills in half and taking them more often. That's what my doctor advised.
Pyridostigmine is a stop-gap medicine and can usually be reduced or eliminated as immunosuppressants take effect. I have been off for many years now but still have to pop one periodically to reopen a sagging eye.