While you may feel that this is your fault, your sex life is something you are co-constructing with your partner. What you're feeling right now can be a good excuse to start communicating. Yet rather than talking about what you find unsatisfactory, it can be helpful to envision the sex you'd like to have.
For example, perhaps the sex you're having doesn't include a lot of foreplay. This can be a good opportunity to bring up the fact that you'd enjoy more oral sex. Or maybe you've been going through the physical motions, but your sex play has lacked psychological stimulation. Talk to your partner about what you wish were happening, expressing it in the form of a fantasy.
I also often ask couples to describe the sex they're having as if it's a menu of items. Couples who engage in this exercise are often surprised by how paltry and repetitive their sex menus are. So I ask them to create alternative sex menus. I ask them to think about putting some new items onto the menu. There are so many different types of sex. Some sex is emotional and tender. Some sex is all about the stress release that can come with orgasm. Some is about fantasy and creativity. Create some new sex menus together pulled from each of these different groups.
What's most important here is that you get that conversation started. A struggling sex life is something for which both partners are responsible.
