My first thought is you fried your charge port somehow, but if you have connected to iTunes and can actually attempt to charge your battery, then your charge port is fine. An unfortunate side effect of changing the screen is that sometimes it can affect your battery. Did you power down your phone before beginning the repair, and did you unplug the battery before disassembling the phone? If you didn’t, this can sometimes have a negative affect on the battery. I’ve seen them run completely down, to where the battery has to be completely recharged after a screen change and I’ve also seen where they just don’t have the same life they used to have after a screen change. You might attempt to have your battery changed. If you encounter the same problem, the issue could lie with the logic board. Hope that’s helpful.