DIY Repair, will not charge now

Good morning everyone! I want to preface this post by saying that I am a Mechanical Engineer and am extremely hands-on. Thats why I decided to DIY my iphone.

Story:

Bought an iPhone 4 brand spanking new. ~9 months after getting my iphone, the lock button went out. Under warranty, I got a new one. That lock button lasted ~7 months and I was out of warranty. I replaced the lock button myself and decided to spice up my phone with a white home button (Its a black iphone). Everything worked fine for a while, then the home button started working sporadically. Last week I disassembled the phone again, removed the white button from the ribbon, and put it onto the stock button ribbon. Reassembled the phone, and broke the digitizer ribbon in the process. $35 later and I have a new screen and digitizer. Got the phone back together and the screen was black. Vibrate still worked. Didn't recognize the computer or the wall charger. Took it apart again to look for problems, found none (I may have overtightened the bolts on reassembly, but loosed them this time around). Now the phone will not charge or be recognized by the computer. I hold the power button down and I get the empty battery with a little red flashing with a plug and a lightning bolt underneath it (For reference, its the first few images that show up in Google image search for "iphone battery depleted"). (I've read that this means the battery has under 5% power and needs a charge). Plugged it in for 12 hours. Nothing. I doubt both of my charging cables are broken as they both worked perfectly before.

I have scoured the internet and forums to find help, but I am not finding much help. I see no broken/damaged ribbons, no bend prongs, etc.

Please help me out, as this phone is more essential to my life and work than I realized and I am on day 3 without it.

Thanks for any help and advice!