Has My Relationship Gone Cold ?

Hey I really need some help because I don’t know what to do... Me and my boyfriend have been together for a year and a half now; and for the first 6 months everything was really sweet and we just got to know each other and he respected that I didn’t want to do anything sexual yet. And then after those 6 months we started doing more sexual things and he was constantly getting me to sext him, to still talk about anything we could that we hadn’t already. Just recently , in the last 4 or 5 months or so he doesn’t seem as interested, in person he does ( we only get to see each other every couple weeks as it’s long distance ) but when we talk on the phone , which has become rare now , we don’t really say much . He never asks for pictures or flirts with me , I feel like he has become to comfortable in the relationship, like he has crossed it off his list and stopped trying to impress me anymore....

I really don’t know what to do because i’ve brought it up with him so many times and it always falls back to old ways again. I keep looking at other people and become tempted but I’m not going to cheat so maybe it is time to break up with him as much as it hurts ? ☹️😭