I find it very funny because you're prioritizing your bf dick over three years of togetherness. You're totally crazy to get shocked over it. Small size is a normal thing and it exactly perform the same function like big one. Also I find it weird that you're sharing his size information with your friends? This is how you respect the bond between you guys? Should he trust you ever again?
A genuine piece of advice is that " go back to him and talk about how you rather than making him feel bad"
Sort out your things quietly and decently!
Remember size does matter!! What matters is how he treats you, care for you, respect you and cheer you up when you're low. These are the things that should matter.
Go get a life girl!