Rob,
if you’re going to talk yourself out of becoming a pilot, it sounds as though you don’t want it enough. I spent years getting through pilot training by the skin of my teeth....one thing was for sure, if they wanted to get rid of me then they were going have to do the deed. I would never have just rolled over and given up. The problem with not being a pilot is that you then have to work for a living! Keep the faith and give it your best shot. If it doesn’t work out then at least you’ll know it wasn’t your fault.
PS. I got 8% in my maths mock A level....and you think you’ve got problems!