Pain while running

[Deleted User]

Im 22 years old and ever since i was 15 i have suffered with sharp stabbing pains in my lower left abdomen. One sunday i was playing football and all of  a sudden a sharp stabbing pain appeared when i was running, since that day i had to stop playing out on pitch and play in goal as that was the only way i could play football, soon after i gave up as i became so frustrated with not being able to run. Since then i have seen many doctors, been given an ultra sound, had physio etc and nothing has worked and the doctors do not know what the problem is and ive been told to live with it. The only way i can do any form of running is by pressing the spot where the pain is in and sucking in my stomach, which reduces the pain slightly however i can still feel the pain. I'm getting sick and tired of not being able to do any form of long distance running and would like to start football again. This is sort of my last hope of figuring out what this is, so if anyone has any ideas as to what it could possibly be, i'd be extremely grateful. Cheers.