I've seen metformin as having weigh loss and weight gain listed as side effect. might certain health conditions predispose me for one or the other?

Maybe.: Metformin usually induces modest wt loss of a few lbs. I have never seen anyone gain weight. The mechanism for wt loss is debated- might be related to decreased circulating Insulin levels but may also be due to direct GI irritation / stimulation ( nausea or diarrhea). Any underlying GI disease or "sensitive" gut might predispose you to weight loss.