I feel like i am always sexually aroused. i find a girl and think of sexual things about her, i do this often is this normal? i am engaged.

People vary: People vary in their sex drive, and being engaged doesn't necessarily mean you'll never notice another female. It's your behavior that's important. If your sexual interest leads you to neglect or betray your fiancé (ie, behave badly), consider seeking counseling or therapy. Otherwise, enjoy what is going on in the privacy of your own head.