Severe muscle cramps?

Hello all!

So for the past 2 mornings I have been having severe cramps just under my knee, when I say it’s the worst pain I honestly think it is (at least that I’ve experienced). Its at 4am each time and I wake up screaming. My SO helps me which is good but I’d say they’re like 5 minutes long. Then the next day I can barely walk.... it’s always in the same leg!

I’ve looked at some causes but none apply to me!

Just wondered if anyone could help me 😭

Thank you