Pregnancy. Labor. Childbirth. Motherhood. It's a lot for a body to withstand. So it's perfectly natural for sex to feel different, and for you to feel differently about sex.
You need time to heal and recover after having a baby, especially if you had a C-section or episiotomy. Beyond that, your body is dealing with a number of other changes, from sensitivity around the breasts (especially if you're nursing and/or pumping) to readjustments of body weight post-delivery. On the psychological side, all of your energy is likely being directed toward your baby. It's tough to drum up an interest in sex when you're overtired, overwhelmed, and feeling as if your body is no longer your own.
On the other hand, you have a partner who's eager to resume your intimate life together. And because happy parents lead to happy children, it's well worth figuring out how to reinvigorate your sex life.
There's been a lot of research lately about how desire is responsive rather than spontaneous. Try taking some pressure off of yourself. Instead of leaping into full-on intercourse, focus on arousal-generating activities. Take a shower together. Engage in extended foreplay. Watch porn together. Giving both your mind and your body time to get aroused—decoupled from the pressure to have sex—can help you reclaim your sexuality. You may also benefit from masturbating on your own, experimenting with what feels good to you now. After undergoing so many changes, including hormonal changes, your body may respond differently to varying forms of touch.
However you decide to approach this, be kind to yourself. Becoming a mother is a huge life change. It's only natural that your sex life would change, too.