Ladies.. help.

My bf and I have been together almost 3 years. Have had oral, vaginal, and anal sex. He used to orgasm pretty quickly from oral but now it takes him forever or he can't at all. He says it's because I've let him finish in my vag and ass so it's hard to with oral anymore because it's not as "tight". I get that but now I feel like I got bad at giving him head or he just doesn't enjoy it when I do. Any ideas or tips or help...? Please?