TLDR: Monitor your system with TM and RM, get rid of unused or useless program running in the background and get more memory.
I'm not too familiar with Win 8 but I am sure that you have both Task Manager and Resource Monitor available. As Sgt Tred suggested above, open up RM but also TM at the same time. On TM, the two tabs you want to pay attention to are Performance and Processes. Start with a fresh re-boot of your system then open both once you are at the desktop. . .usually you can get to TM by simply hitting CTRL-ALT-DEL and selecting the choice, then there is a RM button to open that when you click on the Performance tab.
Give your machine a minute to finish installing the initial iteration of programs from reboot and then pay attention to the activity of the CPU. If it is pegged out or has excessive activity, click on the Processes tab then the Memory button. . .this will display all the processes running on your system based on memory usage highest to lowest use, or click again for lowest to highest. Since you did a fresh re-boot, both of these "should" be minimal for your system but note anything with high numbers. For example, the process explorer.exe is the basic desktop and typically will run about 16,500k, Firefox is running at about 400,000k on my system at the moment. Other things like Avast! and nVidia stuff are there taking up resources as well.
The point is, these are all the programs and processes running on your system when you first start up, before you even start anything else. Once you start going into your normal activities, these processes increase and consume system resources, i.e. CPU usage, memory, disk space, etc. Even more important, Microsoft has NEVER returned these resources back to the system in anything resembling efficiency once you close a program. As a result, if you are opening and closing several programs your system starts losing these resources to the ether that would otherwise be available. The only thing to combat that is a fresh re-boot.
The next thing to consider is all the things that are running and do you really need them. Some programs are optionally set to start when Windows starts but you may only use this program occasionally so do you really want it taking up resources if you aren't using it? Typical culprits of this are Anti-Virus and other programs that "monitor" your system or install then await your use like 3D graphics, bluetooth, etc. Obviously, some of them you need but there may be some you don't based you what other programs you have installed.Anyway, it's entirely possible that your system is perfectly fine and you just need additional memory since you stream. The obvious solution to that is more memory and typically 16GB is the minimum you should consider but like everything else, the more the merrier.
Lastly, Windows Update was having some serious issues with people causing problems like you described. Investigate if this may be applicable for your system because it still is causing issues for people with every monthly update Microsoft comes up with. . .