If the computer is working in other respects, and the only message you get is "No Internet Connection" when you connect to your wi-fi or router at home, then the problem lies with the connection rather than the computer itself.
There may be a software problem (a virus or some malware) that is blocking the connection, or the computer may not be properly configured.
Blue's suggestion to get someone to look at it is a good one. Before you do, though, look up how much that same computer is selling for. (Go to the library and use one of their computers with Internet service.) If the going price for a "new" computer like the one you have is low, consider getting a new/used computer to replace the one you have. You should be able to get a pretty good price for models that have been upgraded in the last two or three years. Some people get the latest computers the way people used to buy new cars every two years.