You have a sexual arousal disorder if you never get a good physical reaction from sexual stimulation. This means that the woman's vagina doesn't get wet enough and the man has problems with his erection. In order to get sexually aroused, something physical and something mental must happen to you. Changes of the body that usually happen when sexually aroused are: faster breathing and faster heart beat, an increase in the amount of blood in the penis which makes it stiff and the woman's vagina getting wet. These problems often occur in combination with a reduced interest in making love, sexual aversion or orgasm problems. For men we talk about an erection disorder and for women we talk about an arousal disorder. These specific forms of arousal disorders are discussed in other questions.