Oral sex

Every time me and my boyfriend have oral sex, he's the only one receiving. How do I get him to want to give it back? 
Just going to put this out there: I'm a hygein freak, so I know it's not because of poor hygein. 
What do i do? I feel like I've tried everything. The only time he gives oral is on anniversary or birthday? Yet, he gets it a couple times a week.