Because having a child is the most extreme emotionalthing most of us can go through, and it turns your life upside down, whatever your normal mental state is. I think becoming a parent can leave so many of your - anyone's - anxieties, stresses, issues laid bare, as the responsibility and emotion just feels so huge.
And then you have a complicated background to deal with. How you are feeling is not surprising - it doesn't detract from the fact that it is wonderful that you have bonded with your son, and that love and bonding will be what carries you through this. That said, you do still need practical and professional help.
wrt dp - I think one of the best things you can do for a partner, when you are anxious/unwell, is to let them know what they can do to help on a practical level. If you and dp can sit down and talk about what will help, he won't feel so helpless when you hit a dip, and you'll get the kind of support you need when you're least able to articulate it. So, if you can get some stress-relief techniques to help you calm yourself when waves of panic start, teach them to dp; help him work through it with you. He may also be able to do this on the phone if he's not around.
Secondly - your relationship has survived a lot already, and that's a very good sign. I will say, though, that the first year of your first baby's life can be hard - you are constantly second-guessing yourself, and it's critical that you keep lines of communication open. If you are too worried to tell dp things, try them out on us first, to help crystallise and calm your thinking, and then tell him - let him in as much as you can.
Your anxieties are normal ones writ large, if that helps to know. But you will be a good mother because you are a good person, a kind, strong and responsible person, and as days go by it just won't feel so strange to be a mother to this little scrap - it'll just start to feel like he's always been with you.
Have you got appointments set up with your counsellor and psych? Has your medication changed since the birth? If you have any questions about breastfeeding and ADs, post them on here - tiktok and others are usually very good about providing links to authoritative advice.