Talking to bf about losing weight

So my boyfriend and I are by no means an active couple. Were young, 18 and 20. He's always been the "chubby kid" and has no drive (neither do I) to lose weight. I've recently gained 10 pounds and no idea how. I love my bf sososo much but I think he should lose some weight as he has always struggled with his weight and is the odd ball of his family. I want to lose weight also yet have a hard time exercisingn in front of him (embarassed)... Any suggestions on encouragement for him and myself???