Lower abdominal pain in women can have many causes:
Intestinal causes: Intestinal causes like stomach viruses, ameobiasis, more chronic causes like diverticulitis, adhesions, intussusception, ulcerative colitis, Crohn's disease, Irritable bowel syndrome, etc.
Genitourinary causes: there are a large number of causes here too, like like renal pain due to stones, glomerulonephritis, ureteric stone, bladder infections, etc.
In case of females, there may also be ovarian causes, uterine causes, fallopian tube causes and urinary tract infections.
Nerve Entrapment: various forms of nerve entrapment like pudendal nerve entrapment, genitofemoral nerve entrapment, etc will also cause you this type of pain.
As such, a lower abdominal pain could be caused by a very large number of causes. Some reproductive tract cause is more likely for you since you are having a yellow discharge. You are possibly having an infection of your genital tract. It could also be due to causes like ovarian cysts or some problems in the uterus. The other cause that you should rule out is pudendal nerve entrapment or genitofemoral nerve entrapment which can also cause pain in the abdomen and lower back.
You should consult a doctor for this, you should consult your family physician or PCP. You will need to be examined clinically and if necessary undergo investigations like an ultrasound examination of the lower abdomen to find out the exact cause form the large number of possibilities.
For now, you should try with:
Take OTC painkillers like Motrin/Advil one tab 8 hourly to control the pain. You should take it after food as it can cause gastritis. If there is any gastritis, take OTC Cap. Prilosec one cap daily.
Lots of fluids - water, juice, Gatorade.
Avoid smoking, cut down on alcohol, cut down on caffeine
High fiber diet -vegetables, fruits, non processed meat and fish - be sure to take nutritious diet
Avoid fatty fried foods
Maintaining regular bowel movements at fixed time
Regular hours of sleep
Regular exercise - take 30 minutes of walk 5 times a week.
This will help to regularize the system, but if the symptoms persist show your doctor for further investigations.