What's going to happen with my minecraft?

The purchase of minecraft is linked to your account, so you can download it as many times as you want. You will still be able to download the game if your computer breaks.

Since you bought your Minecraft account it is now Premium. You download your game on a website that is minecraft.net
So if you have a broken laptop, then you can go onto another computer and download it and start playing again! So basically you can download almost on any other computer.

Your purchase is in no way linked to the computer but instead on any computer you download the launcher and type in your account.

Your account is fine

But will i lose all my worlds

When you buy Minecraft, it gives you a Premium Minecraft account. You can download Minecraft on any computer and use your account to play Minecraft.

So basically once you buy it, you can use it on any computer.

EDIT: How did he answer his own question?

You will be able to re-download Minecraft onto another computer.

HOWEVER, unless you back the single-player worlds you make off of your old computer and transfer them onto your new you you will lose the progress you have made.

Multiplayer worlds should not be effected, however.