Screen backlight works but no picture

My phones been fully functional for under a year now I can replace screens myself etc but I think this fix might be a bit more expensive than just a screen. For some reason my screen just started flashing between picture and black screen (with backlight still working) if I pressed firmly on top right corner on top of LCD connection the picture on my phone would come back and if I released my thumb the screen would go back to backlight. Now my phone screen just isn't coming on at all apart from backlight. Buttons, touch and vibrate still work and I've tried another screen but the same thing happens. Any help would be appreciated