You need to connect to the router/modem and look at the logs. The log will provide information about the line losses and negotiated speed on your DSL connection.
DSL performance is very sensitive to the quality and length of the copper pair that connects you to the Central Office.
In simple terms you need to isolate the problem to either the PC or the Modem/router. If the Modem/router has negotiated something close to the 3mbps/768kb, then the issue is your PC. If the negotiated DSL rate is much lower than 3mbps/768kb either Verizon hasn't properly provisioned the service, or the copper pair between your premises and the Central Office isn't very good.
Also make sure that the modem/router is NOT connected through a DSL filter, and make sure the other devices (telephones, faxes) are connected through a DSL filter.
I assume your PC is connected via an Ethernet cable, as opposed to wireless.
If you are connected via wireless, there may be someone else nearby using the same Wi-Fi Channel for something else, and simply changing the channel on the router may fix the problem.Wi-Fi operates in unlicensed spectrum, so other services such as cordless telephone may operate in the same band. If they happen to operate on the same channel, neither will work very well.
You should learn about the ping command. It will give you a good idea about whether a particular target (url, ip address) is live and responsive. Start by pinging your route. Typical times to access my router are around .5-.6ms -- your's will probably be slower as I'm running gigabit ethernet. Pinging google gives me an average time of about 4 sec (4000ms) -- I am on the slowest Verizon DSL available (760/130) cause Verizon refused to update their DSLAM (I live in the country.)
Try using ping to isolate the problem. Try pinging speedtest.net and see what you get -- I get about 4 sec. This should help you troubleshoot the problem.