if you are comfortable using java, check out www.pingtest.net
It is a "sister" site for speedtest.net
You may have to run site twice or so if the brower asks you to confirm using java for that site.
It will give you jitter, packet loss, ping times and so forth. Packet loss can also affect how the router connects to the modem. I am just trying to rule one thing out
If you have packet loss that will cause pages to load slowly since it is having to re-request packets and depending on how high will result in a very large time. I know this from experience due to installing broadband at a customers house once and was getting very slow load pages. On the cable side it was geting high packet loss, narrowed down to kink in coax (not saying that is problem), fixed and customer was amazed at their true speed.
Now if you do get high packet loss, try no or "verified" good cable and test straight from modem and not router. If that is good then reconnect router and test via ethernet to router, if that is good then recheck wirelessly or how you normally connect. If it works good from modem but not router you may need to a master reset on the router or router could be defective. Changing out the ethernets may be the issue. If high packet loss straigh from modem and you try a few cables, try connecting with a different device via cable to modem and if loss is present call service provider.
By the way you should have no packet loss
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