Oral Sex Help!

I have gone down on my boyfriend multiple times since we got together ( 3.5 yrs ago), yet he has never tried on me. I have no idea if hes nervous or what it is, but I try hinting at it and even have told him that I want it. All he says is I know, I'll try soon, but he never does. I do not want to force him to do it, but ai have no idea how to help him. I even told him id buy flavored lube if he was scared of how it'll taste, I honestly just want some action. I am getting tired of always giving him blowjobs and never getting anything back. I never actually gave it much thought or cared much, but in more than 3 years I am still the only one that makes myself finish. Please any advice!!