Do you think my PC is overheated?

[Angrist]

No that's not it, my fans sometimes kick in (usually when I've played a game for a while, so I assume it's the GPUs fan).

Ok this is right after playing a game of SC2 (graphical heavy):
GPU: 171°F
CPUs: 153, 145, 138, 140°F.

That's not a very big difference...

[Vampyr]

Those temps are on the warm side, but they aren't ridiculous or anything. You could look up the specification for your CPU and see what the highest temperature it can safely run at is. It's probably quite a bit higher than those temps.