Do I have cancer or a brain tumour or am I paranoid?

All day, I feel depressed everyday for the last 2 months. I feel my heart beating and stomach vibrates. My head hurts a few times a day, most of the day I see dots or flashing lights which get a lot worse at night. At night if I close my eyes I see monsters or aliens, if I open my eyes I see monsters or aliens or other things. As well the little dots and everything around me like the ceiling,curtains all move around like your drunk. I have a voice in my head his name is Jake, he asks me to kill my self and says Im a low life sbag whose life is hopeless, as well he is nice to me and helps me with decisions. And what to do next but he not always their he just comes through the day. Well of it come through the day at different times or at the same time. I can contact him whenever I want the other stuff just comes and go throughout the day but normally something always happening. When I have these things at night which wont go away my body nerves make me move like jumping in air of the bed while lying to a different possision. Yesterday night a monster attacked me while my eyes closed and he whacked me in the eye! I'm only 17, and I'm not doing drugs. Iv lost 5kgs in a short amount of time and I eat a lot. I think about 6 months ago I was just under 50 kgs so about 49kgs now I'm 46 kgs and Iv been eating a lot of food apart from breakfast. I have a cough and a cold. Iv felt emotional for ages and about 1 hour ago I just broke down and started crying. I either feel really emotional or 100 people could die around me and I wouldnt drop a tear.