My girlfriend passes out and sometimes has heavy convulsions after sex. it lasts for up to a half hour, off and on for both. should we be worried?

Absolutely: If shen is truly having convulsiops she needs to see a doctor asap.

Post Coital Epilepsy: You do not need to worry unless you do nothing about her condition. You use the plural to describe her seizures so she should see a neurologist to get her properly diagnosed and subsequently treated. Please do not wait for more events as you do not want her brain to "learn" how to have seizures. Good luck and take care.