Can't Connect To Internet Via Wifi Only Works If Use Cable

my computer just randomly stopped connecting to the intenet. I checked my other computers and phone and found they were all working fine. I was having internet problems pior to this happening (internet was being very slow and some web pages and some videos wouldn't load. I think the latter had to do with flash player though.) I had also been doing some stupid stuff on my comp that I know can give you viruses. Furthermore I also knew that due to previous virus's I was not able to do a restore. So as you have probably gathered my computer was pretty buggered even before this problem. So decided to restore to factory default using some backup images I made when I first got the comp. That went smoothly however the internet stilll doesn't work unless I plus it in using a ethernet cable.