So your computer gets good speed elsewhere but not at your own home with your own internet? Then there is a problem with your internet. You need to contact your carrier/service provider. See if the speed issue is on their end or if it is the modem/router that is the problem. If you own it, then you may need to replace it. If not, then make them replace it.
Oh and don't let whatever tech you get make you think it can't be the service. Sadly, with some companies they do that. Try everything to make out that the problem is not them. If you need to, ask to speak to someone higher, but make sure they actually fix the issue.