PC started running very slow after Windows 8.1 bootcamp install

My pc started running very slow when I connect it to the network after Windows 8.1 bootcamp install. Can’t download any Windows updates and navigating the Windows UI takes forever. I can use the PC after a reboot without a network connection but can’t run Windows Defender scan. I tried running rkill, TDSSKiller, Malwarebytes, JRT, AdwCleaner, CCleaner, and KVRT. Can someone give me some pointers for resolving this? It might be a Trojan but need to be sure before I do anything about it!