have a three year relationship with someone. But lately, I've been feeling confused

I have a three year relationship with someone. But lately, I've been feeling confused about somebody else. And it's not physical or something. It's more than that. It's very intense. But I'm 100% sure I won't cheat. I just don't know what to do. Should I move on and try something new or just let the confusing feeling move on on its time?