I would suggest having the codes read with a diagnostic scanner. (This is usually offered at Autozone for free). This will give you a better idea of what is causing the issue. However with the complaint and symptoms you are explaining I would suspect a faulty BAS/ESP control module which is now engaging your Brake Assist function (BAS). Literally the feeling you are getting is this module applying your brakes for you. Under normal circumstances this is only supposed to function in cases that the vehicle feels you are making a panic stop. When this happens you rapidly lift your foot off the gas pedal, and because of this rapid movement the vehicle begins to apply the brakes before your foot even hits the pedal. However now since it is malfunctioning the BAS function is working when it shouldn't be.