Am I bad at giving head?

I gave

my boyfriend head multiple times but here recently he can’t cum for it. He always wants to have sex when he’s about to cum. Use to he would cum really fast with oral sex now he won’t. Is it something that I’m doing wrong? He says I’m really good at it and it feels good he has just built a tolerance. I still can’t shake the feeling that I’m doing something wrong but I’m not doing anything different from the other times. Can you anyone give me tips and advise on how to make me cum faster (he’s uncut)