First of all, ((((HUGS)))) to you. And it's kind of funny; my kids called nursing "Boobie"; so I have all these memories of my boys crying "boooooobie, boooooooobie", whenever they got hurt or got a boo boo or whatever.
I've been where you are, except that the man in question was my husband and we had 3 kids together. And I have lived and struggled with clinical depression for 22 years, but have had medication and therapy, and have been a highly functioning working mom, despite all my problems. You can too! It sounds to me like you don't even like the person you are in this relationship, and that you want to make some positive changes. Can you discuss with your guy the idea of separating? Is he reasonable; does he know you feel this way? If not, tell him! That would be the first step. But you need to become more independent, with or without the guy. He needs to know you want that. You might not have SAD if you lived in New Mexico or something. Or in the Central Valley of California, where it's actually affordable to live because it's so hot half the year. Just decide on a first step, and take it. I have to do that today, myself. I have a whole household to move in one week; and I have to pack the first box. So choose one box, and pack it! Just make one foot go in front of the other. If you can't, seek help! Do you have a really supportive therapist? There are so many ways to find help. It is so hard, but since you really have the will, you will find a way! Keep us posted. Your posting really touched my heart.