Ok so i've been singing for about a year now, ive gotten along just fine and now i have started screaming along with it. It isn't causing any damage, i don't think considering i feel no pain.

My lies is it ok for your voice to be tired after around 2-3hours of screaming/singing? I used to be able to go just about all day with singing so i'm not exactly sure if something is wrong or not.
2-3 hours doesn't seem too bad. Screaming is pretty intensive compared to singing, and if you've just recently started screaming then it's not out of the ordinary for your voice to get tired after 2-3 hours.
The best way to gauge...

Do you start sounding hoarse? If you do, your voice isn't just tired. It's being damaged.

Could I get some more talent in the monitors, please?

I know it sounds crazy, but try to learn to inhale your voice. www.thebelcantotechnique.com

Chris is the king of relating music things to other objects in real life.