My computer seems to be blocking my access to internet banking. It has been a few days now. Is this a virus?

My computer is very slow. I am sure there is a virus or something. I am going to save all my files and reboot my computer. My worry at the moment is that I cant fully access the internet. I cant access my bank accounts online and sometimes I cant access hotmail and other sites at random. Has someone been hacking my computer or is this a virus or something I can fix. I know I clicked on 2 links which I thought were connected to microsoft but realised too late that they probably werent and were some kind of pop ups which looked connected and legit.

Is there anything I can do to check what the problem might be before I need to get someone to look at it – and charge me a fortune!

Thanks