Reported initial connect speeds won't necessarily be dependable or even comparable from modem to modem or location to location. Another problem is that software may report the receive speed for certain modems and the transmit speed for other modems, which can be substantially different. Unfortunately, it is not possible to monitor the actual modem speed during the connection for most modems. Regardless, the only thing that really counts is net throughput, which can be measured by many communications applications. Watch out for heat.
Some modems work better cold than hot, and vice versa .
Generally speaking it is a good idea to make sure that the modem does not get too hot. This will at least tell you whether the problem is at your end or the other end of the connection. If you have your modem connected to the phone line through a surge suppresser, try it without the surge suppresser. Many surge suppressers can interfere with modem communications. If your connections are better, you have a premises problem that you may be able to isolate and fix.