My internet seems to stop loading pages, files and updates halfway through, what is wrong?

[moooo]

It doesn't seem to be a problem with my connection itself - I have a phone and a second, older laptop that work just fine. My newer laptop, however, seems to have started not fully loading things. Sometimes, pages stop halfway through and are just missing parts, or the formatting is messed up. Sites like youtube or flash games sites which continue to load after the page itself has stopped loading don't work at all. It's not restricted to my browser either - windows update don't work at all, nor will updating steam games or MMOs - the speed just drops to 0 after a few minutes. Avast and malwarebytes havent found anything, so I'm not sure what the cause is or how I'd go about fixing it. Suggestions/advice?
I've already tried checking all my browser plugins etc. It's happening to the entire machine, having tried chrome, firefox and ie, as well as having trouble with windows updates, downloads for steam/origin and guildwars 2 updates.

[Veronica Evans]

Hi maybe you need to update your flash or whatever you use, or your videos won't play. and have you cleaned and defraged it lately?
Go to start search for defrag and it should explain what to do.

[Boss]

You might have to contact your ISP.