I have had my HTC Inspire 4g for over a year now, besides it occasionally freezing up, I've never had any problems with it until now. Over the past few weeks I've noticed that I'd leave home with a fully charged battery, and go to school without using my phone at all, and my battery level would be down as if I'd been using it for a while. This has been going on for some time now and it still is. For about the past few days' (at least 4+ days for sure) my phone would not charge unless it sat in one spot without moving. Now, my phone wont charge at all. When I plug it, it lights up and then 3 seconds later the screen goes black and the amber colored charging light goes out. I talked with one of the online AT&T tech support people, but she wasn't much help. All that she said was that it could be the battery or the port on my phone. I don't have the money to buy another phone. What should I do?
Rapidly diminishing battery life, then a dead battery (won't charge) sounds like a bad battery to me.
Although the part about it not charging, unless it stayed in one spot is suspicious (suggests a damaged MicroUSB port or charger). Did you try a different charger? Any MicroUSB charger will work, and most phones (aside from iPhone) use that port nowadays (as well as Bluetooth headsets, and other accessories). So it should be easy to find a friend/family that has one. Make sure you are using the wall charger, and not charging off a laptop or desktop computer USB port (which charges much more slowly).
You can get a replacement battery for around $10 on eBay. For 10 bucks, its worth a try, anyway.