First, let me assure you that you're not alone in feeling a loss of libido: It's common for women to lose desire, even in great, emotionally supportive relationships.
Low desire is challenging to treat, because we women are complex sexual creatures. I prescribe testosterone for some of the women in my practice; about 60 percent of those who've tried it have found that it does boost libido. I wish it were 100 percent, but it's not! And some physicians are reluctant to prescribe testosterone for women because it's "off-label."
Given what we know about women's sexuality, I advise women to engage "mindfulness" when it comes to sex. Often, we feel desire somewhere in the process of being intimate; we may not be driven to intimacy by desire. We need to choose to be sexual! I encourage women to plan for sex, committing to a frequency that is comfortable for both partners. It might be once a week, once a month, on Friday evening or Sunday morning—whenever you're least likely to be distracted, stressed, or tired. When we have been sexual, we've typically found it pleasurable and we're glad we did!
Finally, you mention being self-conscious about your breasts, which are no longer like they used to be. We are our own worst enemies when it comes to body image, and we pay the price when we rob ourselves of pleasures! I'll bet your partner doesn't look like he used too, either, and that he loves every inch of your body, as you love his. You might reread this blog post on body image and try some of the suggestions to "send your body some luv."