What would cause a horrible pain in my left side back towards my back?

I am a 14 year old female. About 4 or 5 days ago, I had these unbearable, killer pains in my left side, right under my rib cage. It would come every 45-60 seconds, and would last around 30-40 seconds. It is so bad that I cry and holler when the pains hit. It's almost impossible to breathe without feeling like I'm dying. It is so bad. Then after about 2 hours of this, when I was about to go to the hospital(I kept putting it off, hoping it would go away) it slowly went away, and I felt fine. During those pains, I had a migraine, and nausea. And after it went away, I didn't have anymore pains, except a few pains here and there, but nothing too serious. And today, it's 12:44 am, about 20 minutes ago, I started having these pains again. Except, it's not near my rib cage anymore. It's still on the left side, but it's back towards my back. The pain is about 2 inches below my rib cage, and it reaches all the way back to almost the lower middle back. It is constant, but it isn't too bad, yet. From 1-10, it's a 3-4. But this is what happened last time, also. It steadily got worse over a course of about 30 minutes. So, I'm really scared! My mom is in bed, but if it gets too bad, I'm gonna have to wake her up and go to the ER. But does anyone out there know what might would cause this? I don't believe it's cramps, I've had all kinds of cramps, and the pain and feeling is NOTHING like this. Also, I don't believe it is being "backed up" because I have had occasional diarrhea all last night and today. Well technically, the day before yesterday, and yesterday. But still, it's getting worse as I type. It doesn't hurt too bad to breathe, but it gets worse everytime I move a different way. I am currently on my bed, with my back against my headboard, and my legs stretched out on my bed, with 2 pillows behind my back. And my laptop in my lap. But it's getting worse, it's about a 5 now. I need help, please. Answer ASAP, please. Or e-mail me at my new e-mail address, jazzyjordy@windstream.net Thank you, please hurry with any advice, or causes!!