Relationship anxiety

So I'm having really bad anxiety about my relationship. This guy I'm with is amazing, he treats me extremely well, he is very romantic, he's handsome, he's just perfect. However whenever I'm in a relationship, I just feel like running away because I'm scared. I'm scared of being hurt, hurting him, if this is the right thing, it's just so scary. How do you guys get over this? Is it normal? Any advice would be amazing.