Why isn't my iPhone Opening even if it says its charging?

Yesterday, my [#|Iphone] 6+ was working fine, I was able to play games and stuff. So I charge it and slept, I woke up at 4:00 am and saw that it wasn’t charge anymore and my mom is charging her phone. So I took my phone and saw the battery percentage was 3%, so I restarted my phone. When it restarted, it showed that the battery low battery. So I charged it, after a little while it opened but it only showed the background picture without the time and date and closed again saying that it is low battery. I went to school and charged my phone at home all day but when I came back home today and opened it it said that it was still charging. It took the charger off and it says again, it needs to be charge because its low battery. Is the charger the problem? because my mother also told me that last night her phone says its charging but the battery number don’t increase. I need an answer ASAP, please.