Boyfriend calling me fat

So I’ve been with my boyfriend for quite a while and I’m a very active person. I’ve always been around 100-110 (I’m 5’2) and never did anything like starve myself or such I’m a cross country and track runner and I used to have a fast metabolism.... in the corse of this year I’ve gained 25 pounds. I’m about to go into college and made the cross country and track team but I am not getting fat on my stomach and my legs do not have a thigh gap at all anymore. We are distance now and have been since August because he’s in the marines ... he told me he called me fat because he noticed I got bigger and wants me to slim down but I’m doing all this exercise and such.

I refuse to send nudes and I want to hold back on sex when he does come home because if he thinks I’m unattractive then he shouldn’t see me like that.

I think this is just how I will look no matter what and it makes me self conscious. I’m also 18 so I think this is just my lady curves coming in but still. Thank you for listening if you made it this far guys I appreciate it 🥺