When you experience a slow or inconsistent Internet connection it is often difficult to gather the needed information and determine the problem, but the answer is easier than you may think.
Computer networks are by design contention based networks. This means a network is shared by many and all network traffic for the many has to somehow contend to survive. The majority of the problems experienced by home users and indeed some corporate network users fall into two distinct camps. The first and the most common is congestion. The second, and hardest to prove, is regulation.
The congestion problem is simply that. The ISP network that you use has too much network traffic and this causes inherent delays to your data packets. This is synonymous with public roads in rush hour, when too much traffic at peak times causes excessive delays. The solution is simple: do not drive in the rush hour unless you have to if you want to avoid those delays.
The regulation problem is a natural counter to the congestion issue and again this parallels public road use in the real world. ISPs intentionally regulate your network traffic flow in order to provide a balance for all the other network users that share your connection to the Internet. For the public roads, traffic authorities create regulation methods which, similar to network traffic, are designed to keep the traffic flowing when congested, traffic lights are a good example.