Do you drink coffee? drink beer? drink sodas, or eat aspartame, nutra sweet, anything with chemical preservatives ? work where there are chemical fumes?
Any of these things can lead to Estrogen dominance. This can happen to females and males.
Testosterone is the hormone that leads to arousal and libido. In the presence of the things above, testosterone will convert to estrogen.
How is your stress level. At times our adrenals can be exhausted and not make enough testosterone.
Emotionally, how are you feeling? Any psychological traumas you are supressing can lead to problems in your sex life.