To add to what others advise, see a doctor!
I will say that if you changed ‘what’ you eat that might be causing problems. There’s a product called soy curls (basically a type of meat substitute) that gave me awful, painful cramps like you’re describing. Following some advice online I added baking soda to the soak water (it’s a product that needs re-hydrated) and it took care of the problem.
But your situation sounds different - I hope you see a doctor!
EDIT: if you have trouble affording it you might want to see if any local hospital systems offer free or reduced care for low income, or reduced care for people paying cash/people who are uninsured. Might want to ask people in your city’s subreddit.