Mass-like sensation under left rib

[Marthreb]

Hello and thank you for reading, excuse my long-ish post.
I have had this issue for several months..
When lying down, particularly on my right side, I can press near my left rib and "push" in a non-solid feeling type of "mass" near the edge of my left rib (towards my center). However, lying on my left side can prove uncomfortable too.
Tested negative for h. pylori months back.. the sensation is like pressing down the safety seal of a jar lid and letting it pop back up.  It doesn't hurt initially, but after a few times can be uncomfortable. I can also feel this "mass" bounce/pop when stretching my torso upward at times, for example, if I am sitting slightly slouched and then erect my torso I can feel the popping/bouncing sensation. It's as if it pops out and then back in to something, like I'd imagine a hernia to do.
I am 128 lbs and 5 ft so somewhat overweight, female, and 21 years old. Rather sedentary lifestyle.  I drink most days, a glass or two of wine a night.
I have a history of left quadrant pain, particularly with digesting spicy foods (my organs feel as if they burn from the spices and it mimics a cramp), if that helps.
I don't think it has anything to do with my ribs. Earlier I was pressing this thing, so for a while I had sharp/dull pain mix under and beneath my left breast. I am laying down now because I'm still having slight pains in the area, and can feel a lot of gas / movement. It radiated to my back earlier as well. I believe the pain was in relation to my pressing of the mass. When it does hurt, the pain radiates some in the general area, and is definitely beneath my rib cage. Sometimes when it does hurt I have the desire to press my back left ribs quite hard, but I don't.
I am worried of a tumor, though I personally think it could be gas (doubtful though) or a hernia (though there is no visible hernia).
I have an osteochondroma (based on x ray they said it was benign), but this thing is beginning to make me worry that they misdiagnosed me and that I've a sort of cancer that has spread..  
Does anybody else have this problem?
Hoping to schedule an appointment soon, though not feeling too confident my doctor will take me seriously - I had to demand x-rays for my bone tumor last time, because my doctor somehow couldn't feel it although I could and she thought I was wrong. I will try anyway, though, and be demanding as I was. I just want some opinions.