I don’t feel comfortable giving my boyfriend head

I have been with my boyfriend for 6 months but we been sexually active together for only 3 months. When it comes to sex he gives good head and the sex part could be better but idk how to tell him that it could be better. Any advice on that? Also lately he has been sending off signs and that he wants head but I keep avoiding them because I’m scared and a little uncomfortable with him basically. But I just don’t understand how I have done it to people in my past and didn’t have a problem with it but when it comes to him I just can’t do it!

Any advice?