Androgens like masteron increase resting muscle tone and promote the ability of a muscle to contract, thats how you get the hardened appearance and strength gains. If you’re already prone to cramping, the masteron might be tipping you over the edge
Look for low-sodium table salt, it’s a blend of potassium chloride and sodium chloride, aka “electrolytes”. Try baths with epsom salts for the magnesium, especially before a workout.
I’d suggest oral anabolics but those are even more cramp inducing than injectable stuff. If you can’t do eq, tren, deca you don’t have a whole lot of other options. Maybe gh if you can get it