Thank you for your reply Marcia!
The pain is located on the lower/middle of the back, usually on my left side. I really haven't had any pain in the front at all. Reading the symptoms, I don't really think I have any others... just the back ache after eating a large meal. It happens roughly once a week/ once every two weeks.
Thank you for your advice on the dr, too. I unfortunately have to visit my dentist first (that should be a fun bill... no insurance for the dentist either; my filling came out because I chew too much gum)

However, I am going to see my dr soon. Do you think it's okay to wait a month or two? The dentist is going to probably cost me a lot, so I will have to save up to pay my dr. The symptoms aren't that frequent...
Another question; is there anything I should be doing now to help? Obviously not eat until I am really full... And I'm going to take notice of exactly what I am eating the next time it happens.
And one more: can I really be having these problems already? I'm only 23!!! I do admit, however, that I am overweight and for most of my life have had bad eating habits... so it probably is possible...
Thanks again!