I'm 18 years old, im waking up with unexplained bruises, im constantly tired, getting headaches, losing weight and feeling dizzy a lot?

Go see your GP: Your symptoms are worrisome and need to be evaluated by your GP. While this isn't an emergency in traditional A&E sense, go there if you can't get in to see your GP.

You need an evaluati: You need an evaluation because this could be part of a systemic illness. The bruising could suggest you have low platelets. You can ask your physician evaluate you for a systemic problem