Sore pain at the lower part of my stomach what is it?

See your doctor. There are too many possibilities to list online. I recommend you see your doctor who can narrow down the possibilities with a thorough history and physical exam.
1/2 my specialty. The answer to this question covers half of what i learned in 14 years of schooling. To hone the problem down, we need to obtain a detailed history, physical, lab tests and possible radiographic examinations. Top contenders are appendicitis, diverticulitis, pelvic and bladder infections, endometriosis, ovarian pathology, tubal pregnancy, etc...