My neck itches every time i shave... why?

I’m 14 years old. started to shave when i was 13. i have a full beard and I’m now starting to shave every 2 or 3 days. However, as of last month, my neck has been becoming very itchy after i shave, and sometimes even stings if i sweat. The first time i noticed this i had tiny red bumps all over the areas i shaved my neck. My friends claimed it was because i hadn’t used aftershave. now i use it, the bumps are gone and the itching has decreased a lot, but still continues… what should i do? i use the Gillette “Mach 3 Turbo” razor, Gillette “Foamy Aloe & Allantoin” foam, and Gillette “Cool Wave” after shave… didn’t notice i used Gillette so much till now…