did you watch your modem lights? (note: the lights can lie, usually don't, but keep it in mind)?
did you go to Website speed test.com to check the page your accessing? it can show you more than just the speed the website your trying to access is serving at (note many websites go down more often than ISP, and many have limits built-in to shut down connections that have lasted too long or used too much bandwidth) ?
Did you hit (assuming win10) Ctr-Alt-Esc) and watch cpu usage, disk usage, network usage? (example: huge hit on disk reads could slow down web browsing)
Did you enable cookies and set your computer's time correctly and flush your web browser's cache?
Did you wait more than 10 minutes after your computer starts (exclude the time in which win10 might be pre-loading sofware into memory or running virus scan)?
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Did you know if you do pin down a regular bottleneck in bps speed that has effected you, that it is traditional for the ISP to refund part of the month's payment until they correct it or change their "promise/contract" for the next month to reflect their ability to deliver?