<human>: Can you give me the gist of the text in a nutshell?

Hi there...I'm a long time lurker. I am seeking advice from your community because I need help telling my boyfriend (let's call him Paul) that his weight gain is starting to turn me off. I want to do it gently as possible.

A bit of backround..we have been dating for almost 1.5 years. We have a great relationship. We never fight, we have a great sex life and we connect emotionally and physically so well. We can talk about everything like rational human beings, we hang out and do a lot of things together and have much  in common.

However...lately my physical attraction to him has decreased. I noticed because [here comes NSFW part] whenever we have sex, his stomach smacks mine very hard and loud. I try to ignore it, but everytime he thrusts  into me it just turns me right off. it's a loud deafening smack. It never used to sound like that. It used to sound like little claps, like someone clapping normally. Now I find it harder to finish during sex. More often I feel unsatisfied and it's starting to take a toll on me.

 When we first started dating, his stomach was pretty flat. He weighed 160 lbs and now he's 200lbs. He is my height, 5 foot 9, and I'm 145. My weight has not changed. Although the past couple months I have been hitting the gym a few times a week (to relieve stress) and I noticed it made me feel really good. I tried to encourage him to come with me but he never wants to. He only has come with me twice that I remember. I'll say things like "it's good for our health. it will be a great way to spend time together. We can show eachother different exercises and even compete too see who can lift more//cycle more".But alas, no luck.

Ive run out of ideas Reddit! Please help me....
<bot>: Boyfriend's weight gain turns me off. Trying to encourage him  to gym it up with me. Never  wants to. Suggestions??