I really feel for you, I have exactly the same problems. I passed my test in September and I'm still not very condfident at all, especially with parking. People say parking is a matter of practice and it's true, sometimes I feel it's down to luck as well, some days you'll park perfectly, others it'll be awful, but once you've done it loads it'll get better.
I went to practice parking shortly after passing, at first at a quiet end of a car park, and then gradually moved up to where there were limited spaces where you had to park in between cars and it really helped. If you're not very confident with parking, for now, park in spaces where there's no cars next to you, and then like I said, gradually start parking in busier areas of the carpark, but only do it when you're ready and you feel confident enough.
In terms of changing lanes, it's always best to get in the correct lane early, but the best advice I can give you is check your mirrors LOADS and indicate, and make sure you know that someone's definitely letting you in before you move over. I once had someone beep at me before I moved into another lane because they'd hung back for so long while I was checking it was safe, but at least by the time he beeped I knew he was definitely letting me in!
As for turning right, if it's busy, then it's busy, there's not really much you can do. If you're indicating and positioned as if you're turning right, then people (or at least someone) should hang back to let you turn in.
It might be worth getting a P plate for your car just to show everyone else you're a new driver. You might find then that people are more tolerant if you make mistakes like stalling. Although the best thing you can do if you're not confident about driving on your own is to just get out there and do it. Honestly, once your behind the wheel in the car on your own, something just clicks and you just sort of get on with it. You find yourself concentrating more because you don't have anyone next to you telling you what to do if you make a mistake or come across something challenging.
Just remember, the examiner obviously thought you were a good enough driver, otherwise they wouldn't have passed you. Good luck!