Is there a kind expert out there who could help me with an internet connection issue

I have a problem with my windows 10 PC in that it wont open some secure websites (not all) I have tried all the usual things that I can think of but something seems to be making windows 10 think that I am using a proxy - the sites most affected are ones with a sign in - eg Windows Store - this wont open in a browser or in the store app. My wb hosting and email provider 1and1.co.uk, any wiki site hosted by wikia.com. I either get an unable to connect message or I get a text only version of the web page which is unusable because the links dont connect. Another PC running Windows 8.1 and a Macbook are runnning on the same router connection and do not display the problem at all. I have been searching for a tool that can analyse my settings to find out what is blocking things. I have ruled out wiindows firewall and my anti virus by trying with these turned off but the problem subsists. Most MS experts tell me to perform a refresh or perform a clean install but I would prefer to diagnose and fix the issue as I do not want to lose my existing software - I have several software giveaways that would cost me a lot of money to re-install as well as one old microsoft program (Image Composer) which runs fine on windows 10 following my upgrade but I know that Windows 10 will not allow it to install as a new program.

I am competent with straightforward stuff but not when it comes to networks and apart from running it I would not know where to begin with this program nor would I know if it is even capable of giving me the information about what is wrong with my connection.