What Causes Bloody Discharge From Mouth?

Ok well it started like a Month ago I noticed after I brushed my teeth I spit out in the sink and in my sliva would be a strain of blood. I thought it was my gums but the more I spit the more I realized it wasn't my gums. I thought it was my throat, but maybe is my sinuses draining in back of my throat? I'm not sure. I'm not experiencing any other symptoms. My tonsils aren't enllarged, I don't have a stuffy nose, I don't have mucus draining in back of my throat I never had nose bleeds. So the more I spit to see what's going on the blood disapears and I don't see blood again maybe until the next day or a couple of hours if I try to spit and try to see blood.

If I just spit normally there isn't blood.
BUT. If I create Sunction in my mouth (it feels like I'm pulling my left tonsil) there is deffinate blood in my saliva and it could vary to a little stran or like a rusty color saliva with a stran of blood. I ALWAYS have to create some sort of suction to spit out blood. So my dilema is idk where its coming from.

I don't have a fever.
I don't have a lump on my neck.
I don't have horse voice.
It doesn't hurt when I eat or drink.
My lungs feel fine. I can breathe normally.
I excercise all the time. So I know I breathe normally.
I don't have a cough.
I don't have ear aches.
**I do sleep with my window open and my bed is under the window and its been cold nights sometimes.

But after I tried to spit out blood all the time cause I'm worried,