Angry over high sex drive

I am beginning to find my behaviour during the regular periods of sexual abstinence in my otherwise happy 20 year marriage alarming and wonder if I am some kind of sex addict, or just a pratt who needs to grow up? I have a greater sex drive than my wife. She makes as much effort as she can, but we can go for long periods without sex. She has phases of not liking herself and feeling unsexy – sometimes this can last for weeks. Despite knowing that she still loves me I always feel rejected...