iPhone Screen Went Black

I was texting my friend, and a notification popped up from her, so I clicked it, but it didn't open the messaging app, so locked the screen. I tried pressing the home button to turn it back on, but the screen stayed black. I was going to try resetting it, but the home button doesn't work, and I don't know when the last time my phone was backed up. Also, when i plug my phone into my laptop to connect to iTunes, it doesn't acts as if it doesn't know it is plugged in. I have an upgrade coming up on July 14th, should I try to fix it, or just hold out? Let me know if you have a solution to my VERY strange problem.

I went to this website and typed in my information. It told me my battery percentage, which was 4%. I clicked on "Lost Mode" and typed a test message, which wound up lighting up the background screen and nothing else. I decided from there, that I should let my battery die all the way down, so I clicked "Play Sound" which was very annoying, but killed my battery VERY fast. From there, my phone died all the way down, so I plugged it in to charge, and it is working again! Thank you +Ellis O'Brien for taking me to this site! Very helpful!