[aith]

I feel like I could have written your post, even today when I am in a fairly senior position and paid an uncomfortable amount of money. My advice for when this feeling gets overwhelming is to just put your head down and get a bit better than you used to be.

I don't mean study really hard, just learn any small new thing and over time you'll improve.

There's no rush and it's ok to be average. The fact that you say the "alternatives seem dreadful" means you are probably in the right career!