Weight gain with Pristiq?

I did a Genesight test and my Dr put me on Pristiq. I have worked hard to keep my weight down my whole life and BAM in a month I have gained ten pounds and the weight keeps going up and up. I can’t seem to do anything about it. I HATE this! I started the med about 3 months ago and have gained 12 pounds. I was on Prozac for 20 years. This is terrible! I would rather go back to that medication.