Sometimes I feel like crap

I've dealt with depression for a long time, the only thing that keeps me going is my children..... I never felt love till I had my first born, and then year's later I had more and being a mother is everything, I'd love another but unfortunately it just hasn't happened and that has left me kinda heartbroken I mean is that a thing?! I find myself thinking about next year as my children with be another year older and my oldest will be 18 and honestly that gives me so much anxiety because deep down I feel he is just going to up and leave me. I had him as a teen so he is my everything. My first love my sonshine literally. Childhood was rough, and it felt as if we grew up together and I can't imagine him not being under the same roof. When he gets mad he'll burst out see this is why I'm leaving when I'm 18. I know it just won't effect me but his younger siblings. Currently my head space just isn't there.. I know just take it one day at a time but I feel like I'm drowning and nobody is there for me. Because I'm constantly the strong one... not by choice but I have no one to turn to. Just laying here in tears and silence but my inner self is screaming.