Why is my dead iPhone 5 still not charging?

My phone usually dies after a short while of usage, but yesterday it lasted longer than normal, and said it was at 93% the entire day, until my last period class. I used it all that period because the class was art and I needed a reference photo for my project. All was going fine until it suddenly shut down. This was normal for my phone, so I didn’t stress about it too much. Then I got home, plugged it in, and went to work on something else. When I came back, about an hour later, and tried to turn it on, then all that would show up on the black screen was a battery with a slim red bar on the left side. I thought it was the cord or the plug (even though I had used this cord and plug several times before) and so plugged it into a different cord and plug. This repeated about two more times before I tried plugging it into the computer, and then into a portable charger, but nothing worked! What could be up with my Phone?