I felt things got so much harder for my mental state after those first 12 weeks. I found talking to other mothers helped and leaning into my support system. If you can get some support - an hour or so to get some fresh air or a nap or to do something that you like may help you feel a bit better.
Idk if this is a helpful perspective or not and I know I don’t speak for everyone. I often wonder why people act like the “4th trimester” ends at 12 weeks. I think that outlook causes us moms to possibly have expectations of resuming normal life or even feeling normal at that point. When in reality that is all going to take so much longer. So then when we don’t feel back to normal, it can affect our mental health where you’re never where you expect yourself to be We are still getting our babies to sleep 4ish naps a day, and so many diapers and so many wake ups at night and we ourselves are generally not physically and certainly not emotionally/hormonally balanced yet. That takes much longer, likely years!
Try to get some fresh air go for a walk