How do I manage bad breath?

I notice even after brushing, my mouth doesn't smell pleasant. I knew then that the odor doesn't really come from my mouth itself. I don't even have cavities. It comes all the way from my internal. I'm so shy to talk to anyone else because I worry this thing. They might smell it and be disgusted. Sometimes, I can see people whom I am talking to moves away there head and I already knew the reason why. Maybe they're too reluctant to tell me about this thing bec they don't want to embar me. I'm har up with this thing. Anyone could suggest a possible solution?