How to tell my boyfriend his breath stinks?

My boyfriend and I have dated for 2 years and his breath really stinks. Some days is better than others but when it does and I have to kiss him, it usually puts me in a bad mood. I am usually really honest with him but for some reason I cannot bring myself to tell him he has bad breath. Its causing me so much anxiety and I don't know why. I know he wont be deeply offended but for some reason I just hate embarrassing people and makes me embarrassed myself and I get really uncomfortable. When I'm with him and think about telling him I get super anxious about it and I literally can't do it. I really don' think I'm going to be able to do this in person and might have to resort to texting it to him. Don't think we're not honest with each other because I literally tell him everything but for some reason I just cant get this out. What should I do? Its stressing me out when it really shouldn't be.