I’m (23) worried about losing attraction on my skinny boyfriend (24). What should I do?

My boyfriend and I have been dating for over 3 years now and he has always been skinny. Honestly, I was never super attracted to his body from the beginning since he is very skinng (underweight BMI), but I’m in love with his personality. However, the past couple of years I’ve been getting very active and hitting the gym often (not trying to lose weight since I’m borderline underweight but I’m trying to tone up). At the gym I realize that I’m very attracted to guys with broad shoulders and bigger arms, not really into six packs or anything but I like guys who look like they lift but enjoy a good hamburger and french fries every now and then.

My boyfriend doesn’t eat a lot because he’s a busy college student, but whenever I’m around I always cook a week’s worth of meals for him. The thing is, when I’m not around he just barely eats anything. I ask him if he wants to join me at the gym so we could work out together but he keeps saying that he hates the gym (he’s basically against gyms). I don’t want to leave him and I will never cheat on him, I also don’t want to straight up tell him that I’m losing the physical attraction (that I barely had to begin with anyway). At one point earlier in our relationship, he said he hated that I had a little belly pooch and that he preferred very skinny model like girls. He apologized for it and he never critized my body ever again. At that moment I just wanted to scream “well I prefer muscular guys but yet here we are” but I held back because I didn’t want to hurt his feelings. What do you think I should do?

Tldr: My long term boyfriend is very thin, but I’ve always prefered somewhat muscular guys. Still decided to stay with him because I’m in love with him as a person, however, I’m losing my attraction but I don’t want to hurt his feelings by bringing this up. I feel really bad and shallow for typing this up...
I’m (23) worried about losing attraction on my skinny boyfriend (24). What should I do?
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