I don’t always cum from sex

I don’t always cum from sex and my wife is starting to feel like it’s an attraction issue. I feel like it’s not fair to use that as a means to deny my attraction level for her. Cumming from sex isn’t always easy for me and I’ve expressed this to her numerous times. Last night we were drunk and she got upset that she gave me head and we had sex but I just couldn’t cum. She has moments where she can’t cum and I don’t get mad saying things like she’s not attracted to me. Someone help me out because I really don’t understand how to get her to understand this