Why doesnt mine craft load when i press login it just stops when it is almost there and now I am just crying my head off because its been happening for a while now so please answer if you know why

It's because your minecraft messed up or something. Don't worry, it' no big deal. If you work through it right you can keep all your saves.
Follow these instructions and you will be fine.
Go to library, application support, Minecraft, and copy, or drag, the "saves" folder on to your desktop.

Now you have to reinstall.

Go back to application support and delete Minecraft. Yes, delete it. Don't do this until your "saves" folder is safe on your desktop.

Now run minecraft again. It will install everything on your computer again.

Finally, return to application support, and the Minecraft folder should be there. Replace the empty "saves" folder with the one on your desktop.

Your Minecraft should work now, just remember there are usually easy solutions to Minecraft :)