What is this left side abdominal pain?

I have had this dull ache and sometimes sharp pain on my left side, i am not sure if it has to do with my reproductive organs or maybe bowels or something but it has been here for a long time, and it doesn't go away for anything... i went to the doctorss and they told me i had a bladder infection, but i didn't have to go pee a lot or anything, so i don't know if thats what it really is...they also said my ovaries and stuff looked normal, do you think they could have missed something when they did the probe ultra sound? please help this pain is really annoying. :(