Game switched to laptop mode even though I play on a PC

I play on a HP Gaming Desktop Computer and recently updated my game to the newest version. I opened up my game to find that I had some UI bugs going on. I closed out and proceeded to check all of my custom content and mods to make sure they were updated as well. After that I clicked to reopen my game and it opened up in a small window and I couldn’t get it back to full screen. I clicked alt-enter and I got it back to full screen but when my game loaded in, the game was lagging and in laptop mode. I changed all of my settings back but my game is still laggy and isn’t acting right. I have tried repairing the game, clearing the localthumbnailcache, etc. but nothing seems to be working. Please help!