Unreal 4 stutters all of a sudden

Hi,
I’ve been using Unreal 4 for a few weeks now and all of a sudden it stutters like there is a bottleneck going on somewhere.

It was working great and it just started. Has this happened to anybody else?
Here are my laptop specs:

intel quadcore I7-4700 2.4Ghz
32MB of ram
Geforce GTX 780M with 4GB of ram
SSD 256GB
Windows 8.1