Very long / half is venting

How do I know if I have this? I've had anxiety/depression since I was a teenager but it hasn't been as bad the last few years. I used to never want to leave the house or be around people (for fear of being irrationally judged but I wanted friends so desperately), I hated myself so much. When my mom passed almost 4 years ago I was forced to be more social. I feel like I blossomed then, though the ugly thoughts still taunted me.
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My son is almost 3.5 months old and all I do is stay home with him. I don't have a car anymore because the frame cracked last month and nothing or no one is close to where I could walk to. I know I need to get out of the house but most of me just wants to curl into a ball. I feel myself back in the same state feeing-wise of when I was a 17 year old girl. I'm miserable. The first few months with my son have been beautiful; I love him. The only reason I ever shed tears is when my boyfriend and I fight, which is often. But today - today I could not handle being around my son. I feel just awful even writing this but I wanted nothing to do with his crying, even though part of me wanted to soothe him so bad. But my boyfriend wouldn't keep him with him, because he's "not feeling well". We've been in a fight the last two days and I've been sobbing on and off. I self-harmed - barely, but it counts (scratched at my arm with my nails when I was alone in my bedroom). I hate myself again. If I didn't have my boy I would love to just end all of this. I'm in the most terrible situation and I don't know if it's PPD or just the fact that my boyfriend and I don't work well. But I have no options; no funds, no parents and no one to take my son and I in. I feel trapped here. I regret having a baby but then I look at him and want nothing else but for him to feel safe and loved by me
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I know I must take steps in order to better my situation. My friend just informed me I will be hired at the same place she works. I'm hoping to be able to save money so I can eventually move out with my son. But in the meantime, I'm deteriorating. Can someone please tell me what is wrong with me?