Should I break up with my boyfriend and move away?

I’m 26, will be 27 in a week, grew up in Denver and moved to the Twin Cities about 6 months ago. I have been with my boyfriend for 4 years, and am felling very itchy and ancy to move on. Overall he is a good guy but I find myself with a very wandering eye. I want to know what its like to live in New York or San francisco or LA, I’m feeling like I still have some wild oats to sew but I dont want to mess up a perfectly good situation… anyone ever been through something similar? Also which city should I go to? Any advice is much appreciated