I was wondering if you have been taking birth control for a really long time and you think you might be pregnant. Could the birth control screw up the results?

What type of birth control measures has been taken , it depends
Explain please

From your short explanation I would assume you mean taking an oral contraceptive, like the Pill.

As far as I know this has no effect whatsoever on any pregnancy tests.

Star :)

There are different failure rates for every contraceptive measures.
Below is a link which will give you your answer,

http://www.emedicine.com/med/topic3211.htm

Cheers :)