What happens after an alpha fucks me? Will i be a sub forever??

Getting fucked by an Alpha isn’t some magic formula for submission. There are certainly Dom Tops who have been fucked in the past, but it didn’t stop or drastically change what was natural to them all along. 

That said, I think once someone gets fucked willingly (even eagerly) that experience stays with the person in some form for another. Sometimes that experience produces more curiosity or even an embracing of submission. 

It all really depends on each individual person.