Hi, I am using my Pi 3 I got with a programming course I have. I'm using it, and the course tells me to turn it off. I do, using the built-in shutdown thing in the Pi menu. I do some circuitry with my breadboard, then power it on again. There's a lightning bolt in the corner, the red light that's built onto the Pi is not lighting up, the green light on it is flickering, and It won't boot. So, I unplug it from the surge protector and straight into the wall. I keep trying, but it won't boot. ONE TIME I got it to boot into Raspbian, but then it went black after 10 seconds or so. Please tell me what to do! It was working before. Just so you know, my sister was using the cord to charge her phone, if that has anything to do with it.