What Causes Abdominal Pain And Blood In Stools?

I am 33 years old Male. I am having pain in my lower abdomen and back side (right side mostly). It is sever in the early morning I get up with this severe pain. It gradually reduces by afternoon; does not completely go away. During sitting when i bend back I sense the pain. When I bend down while standing I sense the pain. I sense like the pain originates from the intestine or colon, and radiates around that place also to the left side. I have acid-reflux history (since 10 years) and a GERD patient. I do get earlier abdomen pain (since many years) and it vanishes after some medication. But, this time it is sever and lasting for months. I found slight redness (blood like) in my stool since few days. I am really worried and the pain is so unbearable at times I get frustrated. Please someone suggest me what it could be and give proper guidance for diagnosis and treatment.