Is it normal not to want to share him?

For 4 months me and this boy have been hooking up at parties and meeting up and having long phone calls. I can't imagine my loge without him. I find him good looking and he'd make a great boyfriend BUT I can never make up my mind in him. He's wanted to be with me in the past but because of my uncertantly, he eventually gave up. We're still close but I still have this small thought of whether I like him enough to be with him. I get so jealous when he gets with any girl or I see him flirting or with a pretty girl. I don't like sharing him. Is this normal? Do I like him? What do I do? Thanks :)