Games lagging/skipping for no reason. Internet and Ping are fine.

Alright, so since last night, I've been having gameplay issues. At first, it was that I kept dcing from the games, but I assumed that was because of the end of the season stuff going on. Then I tried again today, and instead, I'm just having incredibly choppy and laggy gameplay. I tried 3 games today, and every single one I barely had any idea what I was doing and was just pressing keys and praying something was happening in my favor. Forget trying to CS, land skillshots, or even walk in the right place because I could never tell what was happening and when it was actually happening.

It's definitely not my internet, because I was able to hold a Skype call with 3 other people with no problems, and browse the internet like usual. It also wasn't my ping. My ping is normally around 120-150 (damn East Coast) and it stayed there without spiking at all, so what's the deal? Are the servers just screwing up like usual? Are there problems with end of the season stuff going on? It's not just me apparently because when I ask my team and the other side, they appear to be having issues as well. I've tried restarting my computer, my modem even though I figured it wasn't the internet, but nothing has worked. League was working just fine not but a little over a day ago.

Is anyone else having connectivity issues like this? Because it's insanely frustrating to deal with.

EDIT: Now I can't get into games sometimes. It reaches 100% and then gives me an error saying "You have been disconnected. Please check your internet connection and try again. "

My internet is fine, like I said, so this makes no sense to me.