Every morning i wake up have a horrible taste in my mouth. then when i swirl water round my mouth and spit it out it's brown in the sink. help please?

Dental exam: When was the last time you had your teeth cleaned? The dark stuff that you rinse out is blood and foods debris. See a dentist asap. Start brushing and flossing your teeth a least twice a day. This will not improve and will get worse until you see a dentist.

Sleep w/ mouth open?: If you do, it could be a combination of bacteria, saliva, mucus, blood, etc. See your dentist for an evaluation -- at age 20, dental problems can often be quickly and successfully treated.

Chronic gingivitis : Most likely is a chronic gingivitis or periodontists due to a bacterial inflammation of the gums. There is a possibility that during the night you are bruxing (clenching) your teeth and over using the mastication muscles, common cause for tension type headache located over your forehead.