Should I change my migren medication to something else bcause im been taking ponstan and confergot for 10 years plus. What harm if I keep on taking it?

Depends. It depends upon how often you have migraine attacks. If the migraine is severe and frequent then you would be better off taking something to prevent these attacks. There are several meds approved for that purpose. Cafergot (ergotamine and caffeine) is useful only if you have infrequent migraine and its long term use is harmful.