Based on my current knowledge, a Sorcerer with 14 Constitution (assuming you did HP averages) would start with:
Level 1: 6+2 = 8 hp
Level 6: 8+5x(4+2) = 38 hp
But on fastcharacter.com using the same relevant stats (14 con, lvl 6, wild magic, sorcerer), the character sheet shows 45 HP. What seems to be the problem?