Maths Edexcel Gcse Fail - Retakes at Alevels?

Okay well leading up too unit three i got a steady a in unit 1/2 modules. I had overal 169 leading into this exam. I feel i done terrible by looking at the edexcel unit three modules... If everything was at a low i would only get roughly 275 ums! 5 ums of a B I am predicted A's and this is going too look bad on my sixth form app. I was wondering if you think i will be able too resit just unit 3 calc/non-calc again in november as i dont want to do another year at sixthform.

Sixth Form Chosen Subjects: Buissness, Physics, Chemistry, Biology, (retake maths unit 3)

Would this be possible and i just feel terribly unlucky, i felt if only i had a better non calculator and was better prepared i could have easily got 50/60 ums and 45/60 ums on calculator.

I know this may sound stupid but i feel like a failure and embarressment to my family..