Garry's Mod taking ages to launch?

So, yesterday I downloaded a SWEP addon for GMod, and I wanted to test it out.

GMod usually takes a couple minutes to launch, so I went and watched TV.

So five episodes of Family Guy later I still see “Preparing to launch Garry’s Mod”

I tried reinstalling it but that didnt work.

I tried restarting steam but that didnt work either.

So I thought it was the steam servers so I waited until today.

And guess what? It’s still taking hours to launch.

Why is that?