Been feeling nauseous and lightheaded for months and now I just got a bloody nose for no reason. What is wrong with me?

See your MD. Many things could be going on. You need to be seen now -- do not wait any longer. You need to have blood testing to see about possible anemia, diabetes, clotting factor problems, oxygen carrying problems, etc. You have waited long enough already --- do this today. High priority ! good luck and feel better.