Low sex drive

I’m really struggling with a low sex drive, I’m curious, is this something I should be concerned about when ttc? I make sure to have sex around the times that I’m most fertile but after that I don’t even care, I know at some point this will effect my marriage, it hasn’t yet and my husband doesn’t complain because he knows I do a lot so naturally I’m tired (I work a full time day job, go to school 3 nights a week for one class and take 3 online classes, take care of our home and 2 kids and 1 bonus daughter every other weekend and make sure everyone is fed and showered) I’m exhausted. We literally just went a week and a half without having sex and honestly it was only because he wanted to, I could’ve easily just gone to sleep without it. This is all new to me, when we first got together and first got married my sex drive was so crazy high and lately it’s been so down but I’m wondering if it’s just because I’m so tired. I suffer from anxiety, depression and insomnia which really doesn’t help my situation here at all. What can I do to make this better? I want to say sure I’ll just have sex with him to keep him happy but he works so hard to make me happy that I don’t feel like I’m doing my part as a wife here as far as being intimate goes. And I know it’ll just get worse when the time comes that we do add another baby to our mix!