This issue started a couple of weeks ago where I couldn't use my wifi because it was so slow that I was better off using my data connection. When the issue first started I was able to fix it by forgetting the network and entering my password again but now that doesn't fix it, nor does restarting the phone. When I run a speedtest on the phone while connected to wifi I only get whats shown in the screenshot below,

All of my other devices are fine and I usually get what I pay for, which is 20mb down/1.5mb up,

How can I fix this? I've also noticed the phone has been kinda sluggish and buggy at times but restarting the phone usually fixes it. I have firmware 4.1.2 installed and I haven't installed any new apps aside from skype, I uninstalled it but that didn't help.