Alright got it fixed after some hours of research.
I have absolutely no idea why this fixes it though.
What I did: I downloaded java 8u45, and let my minecraft (modded in my case) use this version instead of the up to date one.
Again I have no idea why/how this worked but I hope this post will help more minecrafters. Stay awesome!
Ty for the help that you'd certainly have offered me. This thread can be locked.