Feeling low

I am with my partner now husband for 3 years and he is not sexualy active. Whenever I ask him to make love, he always tells me he is tired. I don't think he's cheating, he's addicted to working out. He's been taking a lot of pressure workouts shakes and pills. Do you think that can cause for him being unactive? Or is it because I am fat and he is not attractive to me anymore? I feel so unwanted. We talked about this many times, but all he does is apologize. What is wrong with me?