Hi, let's take the easiest first.
"...it could be petechiae which is a symptom of leukemia"
When a blood cancer causes easy bruising, it's because of this: the cancer cells get into the bone marrow which is where normal blood cells are made. The cancer cells then crowd out production of the normal cells, which amongst other things results in having low platelets. Low platelets can cause easy bruising. But low platelets would have shown up on a very common blood test called a CBC, which you almost certainly had done.
Next: "numerous lymph nodes in my neck... dont grow"
A cancer most likely wouldn't make a node pop up quickly, then stop growing -- and repeat that over and over. But an immune system reaction is likely to do that. You could ask for an ultrasound, which would show if the nodes look normal inside. You'd also want to see that their shape is oval, not rounded. Moveable is also a good sign. But altogether, a doctor could say there isn't yet enough reason to warrant an ultrasound to be done.
You "also have a rash that's been going on for years that is on my face and chest". I'm not much familiar with what conditions affect teenagers and produce rashes. But all three symptoms are probably related and have the same underlying cause.
All around there is not reason to suspect a leukemia or lymphoma. But I'd want to discover what the real cause is, and not just let it go.
"does this kinda rule out luekimia or a type of cancer"
Correct, there is nothing to point to leukemia or other cancer. You can relax about that, Dylan.