Pain In Side, Uncomfortable To Cough. History Of Miscarriage. How To Diagnose The Problem?

Hi, I believe I have an inguinal hernia on my left side. I believe I have had this since I was a 15 yr old gymnast. I am now 31 and have had 2 children. Since the birth of my 2nd child the pain in the left side has at times been awful. I am a runner and have run 2 marathons (post children). I rarely see a bulge there anymore but it can be uncomfortable to cough at times. There are some occasions where I feel no pain at all. About a year ago I had an ultrasound and they couldn t find anything. I refuse to be cut open unless the dr is sure that there is in fact a hernia. I have also had 2 miscarriages this past year, and feel like the pain is getting worse. My ob has checked me for cysts and any other gynelogical problem and I am all clear, but I am desperate for answers. We wa t a 3rd child very badly, but I wonder if this needs to be fixed first, but what is the best way to go about diagnosing a hernia if the bulge is not present very often?