Don't know what to tell him

So me and my boyfriend have a very healthy sex life. Mostly sex. I'll give him a bj or sometimes he'll go down on me. Over the past few weeks I've noticed I might have an infection or something. Maybe I wasn't being "hygienic" enough or something. But either way I'm self conscious about any different smell or taste before I get it treated or checked out. I don't know what to tell him because he tried to go down on me last night and I was too nervous to tell him why not. Should I tell him about it or just hold out and get whatever it is treated? I'm embarrassed.