How do I tell my parents I want to move in with my boyfriend?

I'm 18, my boyfriend is 24 and they clearly don't agree with our relationship due to the age gap which personally I don't see as an issue, however we live 4 hours apart which is starting to get to me(I'm in love with him and don't want to end it however I want to move closer) I plan to move after finishing my college course in June/July 2014, transferring college to do the 2nd year and my part time job regularly transfer people due to uni, at the time I'll be nearing 19 and will not move until my job can transfer me as I want to be financially independent, I understand and respect my parents wishes and appreciate everything they do and have done for me but i'm worried they'll no longer see me as part of the family and lose contact however I know I'll end up resenting them if I don't leave and do this for me in fear of upsetting them, even if it does turn out to be a mistake. Am I being incredibly selfish?