First, I would change the speed and duplex for Auto Negotiation since if you set Half Duplex this can cause packet collision which result in an unstable connection.
Try to boot your machine into Safe Mode with Networking as this can see if a third party application is causing issues. Also please run a full system scan with your Anti-Virus and Malwarebytes to ensure that you machine is free from malware as this can affect network performance - Malwarebytes : Free anti-malware download
To boot your machine into safe mode please follow this tutorial (OPTION THREE ONLY) - Safe Mode - Start Windows 8 in
Please replace all references of 'Safe Mode' with 'Safe Mode with Networking'