What if there's something better out there..

Me and my boyfriend have been together for 3 years. We spend every day together when we're both not working. He gave me a promise ring when we're were together for less than a year. We have a very serious relationship! I can't imagine my life with out him but sometimes I do have thoughts on my mind like "what would my life be like if I wasn't with him" or "what would it be like someone else" but then I quickly tell my self I'm so comfortable and in love with him and he treats me like a queen I wouldn't find someone else like him. Before we got together he dated around a lot! As in a lot I mean he always had a girlfriend or different girlfriends he had a couple of sexual relationships right before me, and when me and him got together I had never had a boyfriend and I was still a virgin. But sometimes I do think to my self "what would it be like to be with someone else"