Just ONE pound in a month? I wouldn't be worried a bit! Everyone's weight changes from day to day, week to week by a couple of pounds. Weight fluctuates by such factors as eating, water retention, etc. There is no research to prove that ortho-trycyclen causes weight gain. In fact, in the Q&A book I have by them, it says: "Most women will not gain weight. In clinical trials with ortho-tricyclen, there was little to no weight gain reported by most patients."
No worries!