Chronic Abdominal Pain

Needing some help. I am a 23 yo female who is in overall good health. A year and a half ago I started having occasional pain in my abdomin (lower left quadrent). My mother (an rn) said it was likely pain from ovulation so I tried to let it go. As the pain continued I made an appointment with my gyn who gave me a complete exam and could not come up with anything. Since endmetriosis and ovarian cysts run in my family my doctor did exploratory sx. Fortunately everything looked normal. The pain persisted and I made an appointment with my pcp thinking maybe I had a hernia. My pcp ruled out hernia, bladder infection, etc. For the past few months I have been seeing a gastroenterologist; we have tried everything from changing my diet to increasing my fiber intake. I have also had an abdominal ct (which came back normal) and I will been having the dreaded colonoscopyin on monday. Over the past year and a half the pain has become worse and I constantly feel bloated. My stomach is starting to resemble a pregnant woman. Recently I have noticed two new problems: 1) the area where my groin lymph nodes are is very tender to the touch and painful when I am standing and 2) when I have a bowel movement there feels like there is something in the way causing my stool to be narrow.
I guess what I am trying to find out is if anyone out there has had this problem. We have ruled out ibs (after having a bowel movement I am actually in pain; I have to lay down for a few minutes until the pain goes away). The pain has been going on for so long that I am now afraid that this might be something serious. Can someone help me?