Feeling sorta insecure

Me and my boyfriend have been together for 3 years. I have noticed that his sex drive has gotten really low recently. Idk if it’s because I’m just not attractive to him anymore or if it’s because he just doesn’t feel the need to have sex with me. I’m 20 and he is 23 so I don’t think it’s an age thing.

He has lost a lot of weight recently and I read that extreme weight loss can contribute to that? Idk. He was at a healthy weight and now he isn’t.

I’ve also gained 25 lbs. Someone told me that my weight gain plays a factor into it. My weight gain has been mostly in breasts and butt...

He says he still finds me beautiful and sexy and I’m perfect the way I am but I can’t help but to think he has lost interest in me.