Phone turns off whenever power button is touched, can't turn back on

My two year old Samsung Galaxy S4 turns off whenever I touch the power button slightly and it refuses to turn on now. I've searched various websites and most suggest connecting my phone to a computer to put it into download mode, but for whatever reason my phone doesn't seem to recognize when a charger is plugged in. I know my charger is working properly, as it I just tested it on a Galaxy S5, so the issue is with my phone. I had the same issue about six months ago and I was able to fix it with no issues up until now. I plan to have my phone fixed soon, but until then it is still essential for me to use and I need to be able to turn on my phone.