Maybe your router is not capable of doing big speeds? There are 100mb/s, 300mb/s ect routers out there. Are you downloading anything or using a program that's an internet hog? Your family members downloading anything or doing anything? Did someone crack your password and is stealing internet? (Check router logs for anything unusual. Maybe a small DDoS attack)There's also instances of ISP's promising speeds but never delivering, which is why I changed my ISP.Your ISP can also be throttling you. If your ISP is small sometimes it shares internet(don't know the term or how they do it) with bigger ISP's and if that big ISP throttles it's user it forces the smaller ISP to also throttle it's users
was this necessary?
Virus scan?
A ponycigarette must be sapping your internet
ThisYou might have some pony malware, some ponyware, on your computer
I haven't even heard of it.