I had to take the screen off for a sec to reconnect a cable to the screen, and now the phone won't turn on, or restart. I know I didn't damage anything.
does your PC or Itunes detect the phone when plug in?
You might want to do a hard reset.
No it doesn't, and that's what i usually do to "fix" it, but using the sleep/hold button is beginning to be more problematic. It is almost broken, and is sunk down into the phone partly, so I never know if it's actually being "hit"
This is the problem. Apparently, you did not turn the phone off before you took the screen out due to this issue. Since the phone is still live and you try to put back the screen (3 cables involve), you might short circuit some how.
Try to press & hold home button for about 10 second and while holding home button, plug the phone into your PC and see if it wake up.
Unless you know if the logic board is good, nothing we can do at this time.
Do you have any friend who is willing to lend you a phone that you can swap out the logic board to see if yours is still good.
There are so many possibility wrong with your phone.
1. Power button doesn't work. Therefore, you can't turn it on or put the device into DFU.
2. Your Iphone charging dock might be defective.
3. USB cable is also another possibility (this is lightly an issue.
I'm positive mine is still good. The power button is just a bit touchy haha