Hi Ioana,
Dosen't sound like your going through a very good patch at the moment...
I have a few tips that have worked for me when I have needed to see my doctor but haven't been able to look outside let alone step outside without experiencing major panic!
First of all, when you get into the car, put some music on that relaxes you, get someone who you really trust to drive, sit in the seat next to him/her and close your eyes if you need to, I sometimes use to wind the seat back and try to pretend that I was sleeping...
Then if you can do some self talk, you could try to tell yourself that actually I shouldn't feel any different to what I did inside the house, I am safe here, etc, I'm not quite sure what triggers your panic but there must be something you can repeat to yourself... ?!?
A paperbag to breathe in is always good if you just can't cope or you feel you may pass out, maybe your friend can help you do some breathing exercises while your driving?!?
When you get to your doctors appointment, instead of waiting in the surgery, call the receptionist and let her know that you are outside, and ask her to ring you on your mobile when your next inline so you don't have to wait with everybody else and you can try to remain calm in the car...
When you get the phone call, ask your friend to walk in with you, don't worry about what anyone else thinks!, lean on her if you can't keep steady or can't stop shaking, even keep your head down so you don't have to look at anyone but as long as you get there it will be a huge achievement and the next time will be that little bit easier!
Remember the most important thing is not to worry about what you look like to anyone else, your on a mission for yourself, stuff what everyone else thinks!
I hope this is useful, if its too much, try getting your friend to drive you around the block, then the next day try a little bit more etc.
Bye for now,
Angela :)