Could be anxiety I know anxiety gives me stomach pain also could be the meds I know before I was diagnosed with anxiety I went to the e.r. with stomach pain and the doc treated me for giardia (without a stool sample, boy was I stupid) Anyway the meds made me way worse on the stomach pain so you might want to check the side effects of what your taking.
Dude stop taking the Effexor. That **** will kill you.
I had horrible stomach cramps due to anxiety and stress, but i didnt know that at first. I felt like i was dieing and that my stomach had a burning hole in it and gas bubbles were coming out into my stomach (I could even feel the gas bubbles! It was crazy). Fortunatly though, my own diagnosis wasn't exactly possible considering i keep in shape like you do and im young, NO reason at all for stomach problems-except anxiety. So i went to the doctor ive had forever, great guy- very old and experienced, and he laughed and told me it was stress. So i stopped worrying about it and it faded away. I feel it sometimes, but it just felt like severe indigestion or a stomach ulcer or something. Sound like yours? Getting opinions from different doctors helps. Dont ever forget though, that enough stress and anxiety can cause anything. If you worry about your stomach ache- then your stomach ache will probably continue. Anxiety disorders make this stuff worse. Dont listen to everything i say though because im not a doctor,i just know from myself, my anxiety and personal experience. Hope i helped. Stomach aches can be the worst.