havent been able to get on for a long time it says play offline and it crashes if i try to open a world

Put the summary of the bug you're having here
Idk it just crashes
What I expected to happen was...:
Describe what you thought should happen here
i wanted to play minecraft
What actually happened was...:
Describe what happened here
it crashed
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...open game
3. ...play world and it crashes