Electrolytes (Sod, Mag, Potas) are good for their respective contributions which vary depending on your levels and deficiencies, but with Clen what you need in comprehensive fluid balancer such as, and I can't believe you're taking Clen without knowing this

...L-Taurine.
Generally one should begin with 500mgs and increase by said amount as needed. Most are satiated with 1gm, but some go up to 5gms ED, though personally I consider that excessive.
Because your cramping is already so severe, I'd say start with 3gms for a couple of days and reduce daily by 500mgs to 1-1.5gms. ED which should be sufficient.
M.