Can't Access Dashboard

I have my blog on HostGator and yesterday had them transfer it to an upgraded package. I don’t know if my problem is related to this or if it is coincidence, but today I cannot access my dashboard!

When I go to https://www.mydomain.com/wp-admin/ I get a weird looking login screen (not the normal WordPress log in screen, it is as if the page isn’t loading). When I enter my login info, I see my site banner and theme, but the page says “page not found” and then it quickly redirects me to my internet home page.

However, when I try to simply access https://www.mydomain.com I see the control bar at the top of the screen as though I’m logged in, but when I try to access the dashboard or select “new post” or anything similar, I get the same “page not found” and bounce back to my home page. I am having no problem accessing my c-panel, but cannot get into the WordPress dashboard. I have tried clearing TIFs and cookies but that did not help.

I am going to try running a virus scan just to be sure I don’t have something in my computer causing the problem (I downloaded a program last night and noticed afterward that my home page had changed so I think it is possible I picked something up with my download). Has anyone else had this problem, and if so, how do I fix it?