Shaking

Sounds like an anxiety attack to me, I used to suffer horribly with them would go shakey light headed and felt like I could feel my blood going around my body. If I was you id try getting out little by little and get your confidence up with the pram. It used to make me really nervous im also 12 weeks pp but ive been getting out since 3 weeks and am now pretty confident. I used to worry people were watching judging I was doing motherhood wrong which is silly

Speak to your GP, sounds like pretty intense anxiety that would improve with proper support and management. Were you like this before baby?

This is definitely a profound anxiety response, especially the feeling of not being there when you are walking around (derealisation/depersonalisation). I had this for around a year mostly outside the house after I had a significant illness that will impact me for the rest of my life. I found shops/queues/buses or being away from an exit would panic me the most. I would definitely recommend seeing your GP and if you can getting therapy as I felt the talking therapy was really the thing that helped me process what I had been through the most. You may just need to talk/process what a life changing event being pregnant, birth and having a baby is. I really feel for you as it is incredibly difficult thing to deal with. There will be a time that you do not feel like this anymore, please reach out for help!❤️

As a mental health nurse and previous sufferer of awful anxiety and panic attacks…This is definitely anxiety hun. Particularly feeling like you’re not really there/looking down on yourself.
Please see your GP. I wonder if you had a traumatic birth.. not everyone realises you can request a birth debrief which may be helpful for you, I’d get in touch with your old midwife/hub if you think this may help.
In the meantime try to get yourself out the house little and often, to quiet places that you feel able to tolerate. Completely avoiding this will make it harder to face in the long run xxx