My test is just over 4 weeks away, and I'm really starting to doubt myself

My teacher picked up on it today, My confidence is holding me back, and I just know it's going to be the reason I fail, I'm always second guessing when join a main road with light traffic giving me loads of time to react, but I miss judge their speed. While second guessing an overtake today, I accidentally closed in on the safety gap, missed a corner because I was being spoken too, just manly small things adding up, but I'm still doubting myself to be honest.