First off, I am so, so relieved to have found somebody who understands!!
I am one of those obnoxious people who are aiming for straight A*s despite not having a hope in hell of getting it, and I am absolutely freaking petrified. I barely scraped through my GCSE years and I'm still not doing any better, so I know exactly how I'm gonna react to my results and I'm not looking forward to that.
I also completely and utterly sympathise with the second part, but please, let me promise you that it's not true. If you work hard - which you clearly do - then you are definitely going to succeed in life. I'm not going to say you will straight away, but you will succeed.
GCSE results have absolutely no consequence on whether you do dentistry or not. You just need to work very hard, get some help whenever you need it and ace your A Levels / alternative such as IB. I'm not saying you need straight A*s, either - you just need to look into some courses, and then see which ones you like and the required grades. THAT is then your aim. When I said I was aiming for straight A*s, this 19 year old guy who was with me and other 16 year olds on a summer program just laughed and said "You do know that GCSE results are absolutely irrelevant, right?". And they are. We're told they're not, but they are.
I can tell you that you clearly have some self-esteem issues going on. EVERYONE is talented in many ways. Everyone. Also, being academically capable is one hell of a talent!! Don't dismiss that just because that's one of YOUR talents so clearly it means nothing because it's YOU; that isn't how it works.
As and Bs are actually incredibly solid grades, my dear - I go to an academic kind of school, and there are quite a few students who are above average and yet still wouldn't be able to achieve quite that high. So give yourself a pat on the back; you've done WELL!!
Take care of yourself. If you ever need someone, please, just message me.