What Causes Constant Throbbing Pain In Lower Left Abdomen?

Hi, last 2 days I have been having constant throbbing kind of pain in my lower left abdomen. It's not unbearable but it is persistent. Last night had a bit of difficulty sleeping because of this. Motions are OK but a bit constipated - although not much. I initially thought this was linked to my periods pain as I had my period till day before but the pain continues even after the period got over. My family doctor advised I take Ciplox TZ for 5 days - twice a day. Please let me know if this is OK? I had this pain earlier as well - since December 2013 - but it used to come a few days before my periods would begin and then stop in 2 days. This time also I thought it was something connected to that and ignored. But my doctor wants to first rule out any bacterial colic infection before sending me to a Gyneac. I'm also keen to rule this out - pls advise if Ciplox TZ is the right medicine for this pain.