If you think you are not as sexy as you used to be, then there are some things that you might need to change in your life, in order to keep intimacy alive, and to have a great sex life again. Chronic illnesses and other issues might have a negative impact on your relationship, but if you are healthy, then why should loss of libido ruin your need to have sex?
Boredom, lack of experimenting and assuming that you know your partner's body might cause problems like being emotionally distant or losing libido, but it does not have to be that way. If you follow a couple of suggestions, then your sex life can be better.
First of all, communicate. If you have great sex, then it is not needed to say it to you, since you already have great communication, as well, but if you are not satisfied, then you need to give voice to your concerns. If you are worried about your body or sex, say it out loud, but do not forget to mention what makes you feel good, as well. Your partner might know what you used to like, but everybody is in a constant cycle of change. Don't criticize, but rather emphasize what your partner is doing right. And keep negative issues outside the bedroom, where you should rather focus on positive ones.
You should also stay healthy. If you have light workouts regularly, if you sleep well, eat right and do not poison your body, then your body will stay fit to sex longer, so you can experience the sex you want and what you were used to.