Why isn't my iphone turning on?

So it's been a couple weeks since I've charged my Iphone 3S, because we were waiting for a piece to come in since I'd cracked it. Well, today we got the piece and when I went to plug in my phone, that obvious screen comes up that says I need to plug it in to a power source. So I did. And a few minutes later the sliver apple screen came up, and then a loading screen. Then it went back to the screen that tells me to plug it in again. And it's done that several times consecutively. I'm only hoping that since it's been several weeks since I've charged it that it's taking a little while to come back on. But there's also something telling me that's not the case, and when I ruined my screen and digitizer and LCD screen, it ruined something in the motherboard. Please tell me what's up with my phone because I'm really scared.

Try holding volume down power and home button all at the same time until you see the apple logo come up twice then release.