Skins glitching?

Put the summary of the bug you're having here

What I expected to happen was...:

What I expected to happen was I would just play on a server normally

What actually happened was...:
What actually happened was my skin was suddenly the default Steve.

Steps to Reproduce:
1. Log in to Minecraft
2. Log in to Singleplayer/Multiplayer
3. View your skin and see if it's the default Steve/Alex