Muliplayer inventory bug

Me and my friend were playing minecraft together when i logged off again. then when i logged back on while the connection was still open i have the same inventory. now when i log off then the host logs off, the next day when i log on my inventory is wiped and i have nothing but 14 levels (it sucks i had just enchanted my brand new armor and i had a sharpness sword.) idk why this happens but it keeps happening. Please fix it. PLEASE???????

:3 Lmno