Hello!
Thank you for the query.
Lower left abdominal pain can be caused by
diverticulitis, inguinal hernia,
urinary tract infection, urinary tract stones. Bowels obstruction is also possible.
Diverticulitis is caused by
chronic constipation. It can give irregular bowel movements, fever, nausea, etc. In some cases it can even result with intestine perforation.
Hernia usually causes the lump in the groin, pain gets more intense while standing and lifting or coughing.
Urinary tract infection or stones can give also back pain,
frequent urination, burning while urinating, the pain can radiate to the groin.
Bowels obstruction should be suspected in case of gas and stool blockage, nausea, bloated abdomen.
I suggest your boyfriend to visit hist doctor and have some diagnostics.
Abdominal X-ray, abdominal ultrasound, blood work, urine analysis should be done at first.
Hope this will help.
Regards.