Can't look around properly in Viewport

In the blueprint editor - Viewport
When holding RMB+ Moving my mouse around, it will not move in the correct direction, example;

Holding RMB and moving my mouse UP will make me look RIGHT.
Holding RMB and moving my mouse DOWN causes me to look LEFT, but only untill it’s pointing staight down again( like in the picture ).
Holding RMB and moving my mouse LEFT or RIGHT will orbit the camera…

The controls when holding MMB/LMB are also messed up, although i don’t use those.
This is only while in the blueprint editor, and started out of nowhere.

Please help, i’ve been stuck with this problem for a while now and can’t find a solution anywhere!