I would suggest couples’ therapy to get to the root of why. Partners often withdraw from sex because they don’t feel their needs and being met, or don’t feel safe and secure with their partner as sex is a vulnerable act. Something you could do, is make it clear you just want to have some intimacy, no sex, just cuddle, just kiss, to help build up the intimacy again without the pressure of sex. Show that you just want to be close to her, not to satisfy your own needs.