Help!! I need advice

So my boyfriend and I have been together for a little over a year now. Before we got together I explained to him I don’t like giving blowjobs, I have a really sensitive gag reflex and something traumatic happened to me regarding that topic when I was 15. He’s been perfectly fine with it and over the year I’ve done what I can and tried to do my best and give him something but sometimes I can only go for so long and I don’t do it often. But now he’s telling me he wants to be allowed to have other girls give him head and it’s not considered cheating and it’s wrong of me because head is expected of a girlfriend? What should I do? Is he right?