I figured out what the problem was. Coincidentally, my page loading problem started as soon as I installed Kaspersky on my machine.
Apparently, the new Kaspersky update has a problem with Opera's VPN. To fix the problem, simply set opera.exe as a trusted application in your antivirus settings.
Kaspersky -> Settings -> Security settings -> Network Settings -> Configure trusted applications -> Add -> Select your opera.exe -> Check "Do not scan encrypted traffic" -> Click OK.
I just found the solution on Opera's reddit and it worked perfectly (: Hope it works for you too!