How do I tell my parents I have a girlfriend?

well, I met her online on omegle and we started talking over text and skype, we call alot and text alot and we have been dating for three months. I love her so much but I dont know if my parents will except me. She is coming to my town during spring break to visit me and I want to tell them before or when she arrives. I dont know how to tell them, because last time I tried to tell them im bi but I have never felt a romantic way towards a guy, they said it was a phase or hormones or an excuse or a lie or it was the people I hung out with. I dont want that to happen again, but I want to tell them. What do I do?