Launcher not working and not launching the game

Put the summary of the bug you're having here

What I expected to happen was...
I would hit play and Minecraft would launch

What actually happened was...:
The launcher stopped working

Steps to Reproduce:
1. Open launcher
2. Press Play
3. Launcher stops working

On some occasions it does launch, however it then says 'minecraft is not responding' and crashes anyways. Please help this has been happening for a week!!