KB/s fluctuating between 0kb/s to 10000kb/s. No idea what's causing it.

[Boombaka]

https://obsproject.com/logs/0Hy9h2i9I4eAP3cq is log.

I streamed fine 3 days ago, and didn't notice any issues. I added in browser sources from streamelements, could that be what's causing the problems?

 

[qhobbes]

Network congestion is causing it. Your bitrate drops from 6000 almost immediately. Try removing those browsers sources. It seems like they use an awful lot upload bandwidth for overlays or whatever. Stick with the local overlays if you have limited bandwidth, like myself. You can use Task Manager to check what is using bandwidth.
OBS Settings, Advanced, Network, Dynamically change bitrate to manage congestion (Beta) is enabled. You can disable it but it could result in dropped frames.