bad stomach pain

i was just wondering cause ive noticed ive been having stomach pain chest pain and the doctor said i have gas . and its like i feel when i go to use the bathroom i feel as if my stool has blood in it when i look at it i think it has some sight of blood but im not sure if my mind is playing games with me . so just to be on the safe side i was wondering . and i feel like a little cramping in the stomach i been having diarreah (diarrhea) sorry i dont know how to spell it . im 16 years old and was just curious . and ive been feeling light head sometimes . and i feel like i have to go to the bathroom even though i dont have to . thanks for answering my question when you do .