Cramping and diarrhea for 4 days now?

For the past four days i have been experiencing stomach cramps (or maybe bloating?) with mild to moderate severity. The cramps come in waves however there is always a small cramp feeling by my lower stomach/waist. The waves of cramping usually happen every fem minutes causing pain in my entire stomach/gut area from anywhere from 5 to 20 seconds. Throughout this i have also been experiencing diarrhea. The first few days it was not god but after about two days it began to solidify a bit and turn green in color. The cramping today (day 4) was better in the morning but is now worse in the afternoon. The diarrhea has returned and stool color is slightly red. Im a 16 year old male. Any thoughts on what may be causing this and what i could do to remedy the situation?