Without more information regarding you computer, your wireless adapter, your wireless router, etc. We would be hard pressed to offer any legitimate help. Are you sure you are not using some type of mobile broadband adapter to acquire an internet connection. These can confuse some people in that they act like a wireless connection but generally setup like a dialup and their performance is often slow based on your proximity to a 3g or 4g source antenna.
So what is your wireless adapter's manufacturer name, model name/number and revision number? What is your wireless router's manufacturer name, model name/number and revision number?
Are you currently using any third party software to manage your wireless connection? Are you currently using any third party security suites that may be performing any type of state packet inspection? Like firewalls or internet security suites?