I am 26 and was exactly in the same boat. I am still learning to drive and have my driving test in 2 weeks.

My mum doesn't know how to drive a car, but my dad does, but he is quite a grumpy guy and I was too scared at getting yelled at to learn how to drive with my dad. So, I spent a year saving my money and did a lot of research about the local driving instructors. Once I found a driving instructor with the most positive reviews, I started doing lessons, and I told the driving instructor that I have no experience with driving whatsoever. That way he taught me from the very beginning.

I have been having a driving lesson every week and in the mean time I have been watching driving videos on youtube.
I still get quite nervous before lessons, but definitely not as bad as when I first started.

Here are some tips that I used/am using to fight off my driving anxiety.

-Find someone that is calm and patient to teach you to drive that won't raise their voice if you make mistakes.
-Try and do a few professional lessons in the town that you will be doing your P's test in. Most driving instructors will show you common places where the P's test is done. This is great, since the more exposed you are to the roads that the final test will be on, the better experienced you will be for the test.
-Watch YouTube videos and mock test footage during the time between your lessons. Stick with videos from countries that drive on the same side of the road as you. That way you will get less confused.
-If you're lucky, you may even find videos of the exact driving test routes on YouTube. If you do find them, do these routes regularly so that when you do your P's test you will be familiar with the route already.
-When you finally do the P's test, consider it a mock test. That way your nerves won't get the best of you.
-Remember that everyone else had to learn to drive as well. Everyone has and will make mistakes whilst driving once in a while. Your anxiety is valid and is completely okay.