Is it cheating if it's the same gender?

My husband and I have been together 4 years, we have 2 children together. Our relationship is great but the sex isn't that great. Every time after we have sex I have to masturbate after.

I always masturbate to women and it turns me on so much. I used to always think about cheating and doing something with a woman but never went through with it til two weeks ago. I've had this friend for about 2 years and I never thought she were bi until we talked about my marriage and my sexual desires on how I felt. Long story short we ended up giving each other head last week and like twice this week. Would your s/o be upset since it's a woman and not actually a guy? I plan on telling him but I'm not sure how he'll react.