Sounds like your LCD is busted. The way you can check if it is - connect the laptop to the external monitor and if the picture is fine, you have a defected LCD.
Good news, if your warranty expired, there are plenty of the laptop LCD companies that sell them for relatively cheap, depending on the model and brand of the laptop.
The process of replacement of LCD for a laptop is pretty straight forward and the seller usually has step by step process on their website.
Whatever you do, do not buy from the manufacturer of the laptop, their prices are truly outrageous. What makes it ever more outrageous is the fact that they do not manufacture those screens, its usually Samsung, and a handful of other companies. The laptop manufacturer just puts a premium on the top (a really hefty one) and sells it to you.
Also, installation does not require you to be a computer savy person, its usually is pretty straightforward (unless its an Apple, then you will have to map it out)
Source: worked for LCD repair/seller company for a year as a student.