Problem with x-axis

I just just finished building my printer, but i have a problem with the x axis.
I don’t know how to describe the issue so here is a video of it:

drive.google.com/open?id=0B94w4 … jliYWZWU00

Is my belt too loose? If so how can i tighten it?

It looks like an alignment issue.

Look in this link.
http://www.k8xxx-3dprinters.crimed.be/w/index.php?title=XY-Carriage_Alignment