Losing interest?

I’m going to keep this long story short:

I met a guy and we’ve dated for almost two years but recently I haven’t felt the same about the relationship and I guess u can say I lost interest. He’s a great guy but I just don’t feel the same anymore.

So moving on, I met this new guy and it seems like he wants to get to know me and I feel us clicking but I feel bad for having feelings with this new guy when I’m still with the other guy

I’m planning On Breaking up with the guy I’ve been in a relationship with for almost two years but I know it’s gonna hurt him to lose me just because of some “ loss in interest”

Advice?