Keep trying!
Hopefully, you get a week's break followed by some consistent line flying to get you up to speed. Fight your corner, and understand that you are likely good enough with some final investment by the company. They won't want to let you go at this stage.
Same instructor, same routes, allow you to cement a professional technique that you can build on and apply in many different situations through your career. Ask for some consistency to allow you to regain confidence and bed in some good habits.
Many of us have struggled and failed in this business. Checking and supervision is a continuous part of professional aviation, but it can be acceptable without undue stress. Just convince this lot to invest a bit more in you. Success may be round the next corner.