I (31F) love my boyfriend (33M) but I’m fantasizing about other people…is my relationship over?

31F here, I have been with my boyfriend 33M for 7 years, lived together for 4. We have always had what I’d call a ‘healthy’ relationship with great communication, supportive of each other, we go out together on date nights most weekends and laugh a lot together. We have a lot of mutual friends, are financially stable and have a full life together. We frequently talk about marriage and kids being in the near future.

One issue we’ve faced which is becoming more and more of an issue for me is my boyfriend’s insecurities. He’s a good looking guy, however, he hasn’t been in ‘great’ shape for a long time (although I wouldn’t say he is overweight) despite going to the gym. He goes to the gym because he feels he needs to, and isn’t really passionate about any sports etc. on the other hand, I absolutely love the gym, it’s my main passion in life - me and him used to share this passion but in recent years he’s fallen out of love with it. Where his insecurity is affecting me, is he doesn’t feel comfortable with other men in the gym spotting me when lifting heavy weights, he gets funny about it (we go to different gyms so he can’t spot me) I would never be able to admit to having a celebrity crush as he would be jealous, he gets funny about me being friends with guys at work etc…sounds really small, but it can be a bit frustrating as I’ve given him no reason to not trust me. I am not jealous or insecure about his female friends or celeb crushes as I trust him and am confident in myself.

If I’m honest…now I’m in my 30s and am confident in who I am as a person and am very secure, being with someone who is insecure like this isn’t very attractive. I try and be his biggest cheerleader but when I tell him I got a new PB at the gym his first question is “who spotted you” instead of congratulating me. I love him as a person (except the insecurity parts) and he makes me so happy day to day, but there is a spark missing - I don’t want to rip his clothes off despite him being attractive, and haven’t for a while. However, we are very affectionate - we have sex regularly (it’s good but I don’t feel excited about it) I cuddle and kiss him a lot and make him feel loved, and tell him when he looks good. So I think I’m doing everything I can in that sense.

I didn’t think too much of all this until recently, as I was content enough - although it has crossed my mind ‘could I be happier’. However, in the past few months I’ve met two people through the gym who are very into fitness and share my passion, who really take care of how they look, and I’ve felt a spark. One was a few months ago and I no longer see them at the gym, one was very recently. This has ended up in me fantasising about them and imagining not just sexual encounters, but thinking would I get more excitement out of life being with someone like them. We don’t flirt or cross any lines, but I do feel some chemistry between us - they are attractive and we chat about common interests, and I look forward to speaking with them as they hype me up at the gym and make me want to better myself.

I’m freaking myself out because I love my boyfriend and would never cheat, but why am I having these thoughts? Is my relationship doomed? Do I need to break up with him? How do I tell him that insecurity is not sexy, and I feel like something is missing? He has no idea how I feel, and I feel awful. I’m worried that I will never get over this fantasy of wanting to be with someone who I find more physically attractive and who shares my passion, and is secure and confident. But I also don’t want to throw away my best friend because of a fantasy.

TLDR; I love my boyfriend but his insecurities are driving me away, and I’m wondering if the grass is greener elsewhere.