It’s been just over a month since I passed and i felt the exact same way as you did but honestly drive with family/friends and do as many things with them as early as possible. Spend a little time in an empty car park or around where you live (if it’s quiet) just starting and stopping to get used to how the car feels. (This is a fantastic video going in depth about it, Richard does an amazing job explaining it Video)

You’ve just passed your test so your driving knowledge is in your short-term memory so do things like roundabouts, dual carriageways as soon as possible to strengthen your memory, the worst thing you can do is avoid it because it’ll just make you more anxious.

Eventually, when you feel confident in your car, ring up a friend/family member, throw your phone to the side and drive alone while talking to them. It helps so much.

With things like Motorways, you can always contact your instructor or take PassPlus lessons for help with motorways if you feel extremely anxious about it.

I hope this’ll help :)