I have a low-ish red blood cell count of 135. is that dangerously low? would there be any symptoms at levels like that? headaches? etc.

Low blood count: what is your Hemoglobin? You should have at least 4.5 million cell/ml of blood, so 135 million cell/ml is too low. provide us with the whole CBC count.

Definitely lower: If your rbc count has been that low for a long time then you may not even notice symptoms because the body is very good at adapting to this condition over time. Common symptoms include easy fatigue/loss of energy, shortness of breath and headache with exercise, dizziness, difficulty concentrating, skin paleness,and leg cramps. Other symptoms for more specific kinds of anemia do also occur.