Should i avoid starting a serious relationship with this guy?

You're still 18 and young. True love waits, if he can wait for you, he truly loves you. That's a good thing not easily fooled by his "I love you". Enjoy your single life for awhile and have fun with your friends instead. Time will come, your real prince charming will be there for you-- who have survived the waiting compared to other guys who easily have given up.