I donated blood yesterday. then today, i went to my cycling course and had chest pain, shaking, and sob. i feel fine now but should i get checked out?

Anemia: Because of loss of the unit of blood and loss of blood in the cycle your blood pressure and hemoglobin are likely low. Please drink an electrolyte rich drink such as gatorade or powerade, keep yourself well hydrated, rest for a day or two and get your CBC checked. You may need iron supplementation. If these symptoms happen again, please consult with a physician.