What happens if you take more amoxicillin than prescribed?

No. It won't make any difference; antibiotics are carefully manufactured to provide the optimum dosage. Taking more will not get rid of your infection more quickly, any more than using more detergent than recommended will make your clothes or dishes cleaner. If you feel the amoxicillin is proving ineffective, return to your doctor and discuss the problem. Remember it is vital to take antibiotics exactly as directed, and to finish the course.