Amphetamines & severe muscle cramps

I’ve been prescribed amphetamines for add since I was an elementary child, but I’ve never liked them. Even as a kid I was clever enough to hide not taking them. Anyway, I’ve always had a prescription. I’m in my thirties now and once I got diagnosed with fibromyalgia they suggested i take them to help with fatigue.

The rare occasions that I do take them, certainly they help keep me motivated on task and awake- sounds great right?

As they begin to wear off i start having the most intense cramping it’s like my body locks up entirely, every joint every chest muscle everything from my neck to my toes. - No it’s not panic related. My mood is fine, if not uplifted.

They didn’t always have this effect on me. Am I imagining the correlation? Is this just how people feel after an active day?

Does anyone else experience this?