Insecure boyfriend :(

My boyfriend has the sexiest body. He’s so big and strong. But he thinks his stomach is chubby (its perfect). Yesterday we were throwing around a football outside and it got really hot but he refused to take his shirt off. It makes me sad. I wish he could see what I see. What can I do to help him with his confidence? It’s almost summer and I don’t want him to feel insecure at the pool and stuff