Is it regret or not real? 😰

My boyfriend and I have been together for 3years now.  So you could say we are very serious in our relationship and we are even planing on starting a family together. When we were together for a year I srarted talking to an ex boyfriend who happened to be my first love.. I kept it from my boyfriend but he found and and then I cut all ties with my ex so my boyfriend and I could move on with our relationship. But for some reason I keep finding myself thinking about my ex sometimes or even having dreams that we are still together, sometimes I think about breaking it off with my boyfriend to think about what I really want but I really do love him and I think I want to spend the rest of my life with him, but I only just turned 20 and I know I want a serious relationship and me and him have it so good.. I just don't know what to do, plus I don't have any reliable friends to talk to about anything because they would just say breakup with him.. When I don't really know if that's what I want to do.. I don't let my boyfriend know that I think about my ex once in a while.. Because I don't want to hurt him when if all I'm feeling is stupid little feelings that don't even make sense or are even there anymore.. I haven't even talked to my ex in 2 years so he could be the same asshole I loved at one point or just even worse then he was when we were younger.. Plus my ex did talk crap about me to some girl he was trying to get with saying that I was the one that cheated on him when it wasn't.. So I don't know.. I guess all I'm asking for is a little bit of reassurance that all this is, is dumb feeling that aren't even still there.. 🤔