Yep. Sounds all so familiar. Hurts when sitting, hurts when getting out of bed, hurts when getting in and out of the car, hurts when pooing (the pushing), hurts when sneezing, hurts when doing ab work including lateral twists, BUT...all calm and not so uncomfortable when lying flat. It could be a SH or AP. May be a tear on one of the obliques or the aponeurosis. May be a tear of the rectus abdominis - lateral, anterior or posterior, not likely a medial tear. May be FAI. OR...any combination of the above. Or, as it was already pointed out to you, an incipient or occult hernia. The groin area is one of the toughest areas to diagnose accurately.
If you haven't gotten their yet, check out Mike Boyle's easy rehab regime to possibly help strengthen the area -
www.strengthcoach.com/public/1606.cfm
There are some groin strain exercises you can work in there -
www.andorrapediatrics.com/ap_folders/hand-
outs/knowledge/groin_strain.htm
Also, there are core strengthening exercises geared toward the inguinal area at the Hernia Bible -
http://www.groin-hernia.com/herniabible/ex
ercises.html
Of course, everyone needs to use a modicum of common sense - if these exercises hurt or are painful, don't do them! (and I wouldn't do them all on the same day either - you don't want to overload the area) They are not designed to be power exercises or to see how far you can stretch yourself, but stabilizing exercises to take pressure off of stressed muscles and tendons that are experiencing the pain by strengthening the remaining good muscles. You're a fitness instructor, you know how this theory works.
Definitely try the rest route before you start down the research road for surgery.