You need to gain some sense of control over your body. Try to spend time remembering good sexual experiences. Work at finding some fantasy that titillates you. Experiment with lotions and sexual lubricants and, if willing, learn about the use of a vibrator. It may be that you will not feel overwhelmed with desire as your encounter begins, but if you are relaxed, feeling good about your husband, sensing that you do not have to fake anything, and have discovered some neat aids to your arousal, you can begin to have sexual experiences that are enjoyable.
Sexual desire is like hunger.
Some people are ravenous, others anorexic. Your level of desire is to a large degree independent of your nonsexual feelings for your husband. Even if he realizes this, he might resent your lack of sexual interest. Remind him that he would not expect you to eat a three-course meal if you are not hungry. However, you might be willing to snack and, in the process, discover that it is possible to whet your appetite.