He Wont Go Down on Me, WHY!!!!

I am so curious to know why I have never been gone down on by my boyfriend.... I have been with my boyfriend for 6 years, and we have 2 children together. We have been having sex for 8 years. We have done every position, I give him oral at least 1-2x a week. I have asked him to go down before be he always says hes not ready. Now I am not one to force someone to do something they dont want to or feel comfortable doing but I am curious to WHY after so long. I clean myself well, and shower daily! I am not a dirty person, I have no STDs nothing!!! I have read some guys just arent into doing it, but I mean wouldnt a normal guy want to please his women too!?!?! help, this really has been bugging me for sometime now. I am not going to ask ever again, I told myself that and I am sticking to my guns. I have only asked once why, and he told me he wasnt ready. He has NEVER gone down on someone and hes 28. I believe that !!