Iphone 4 won't turn on, sync or charge?

My phone was perfectly fine today. Nothing out of the ordinary. Randomly while I was at work it stopped working. I keep my phone in my pocket and i went to go check it and nothing was happening. It doesn't respond to anything. I was just on it maybe 10 minutes prior to when I noticed it wasn't working. It had about 50 percent battery when I got to work and i had been there for not even 30 minutes. I've plugged it into the usb charge and my computer but still no response. I can't do a hard reset because my lock button stopped working a few weeks ago.since then i have been using assistive touch. I've been holding off on getting a new phone because i have an upgrade in two weeks.
I don't know what else to do. Has anyone else experienced this before? Do you think my broken lock button had something to do with it?

That'v very unusual to happen to an iphone. Most problems with the iphone is usually the battery or broken screen. I believe it's probably because of the broken lock.

Just wait for 2 more weeks so you can upgraded it.