dealing with my friends

I'm really tired mentally and physically. but right now I'm the only thing keeping half my friends alive. They all have issues and they depend on me to help them. but I don't know how much longer I can go. I'm barely dealing with my issues and having to deal with theirs also is becoming too much. I stay up late making sure their ok and talking to them and then stay up even later to finish up with homework or other stuff I have to do. leaving me exhausted. I love my friends and want them to be ok but I can't keep this up. I'm barely taking care of myself just to ensure they're okay.