Phone keeps flashing on and off during calls

[Sinful1217]

Wirelessly posted (Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 8.12; MSIEMobile6.0) Sprint T7380)

For some reason my screen keeps flashin on n off during many of my phone calls. i thought mayhe it was because my cheek was right on the phone n therefore touch screen was activated. but even while i was on a phone call i made sure my cheek was not touching the screen n the same thing happened. anyone else experiencing this?