Anxiety meds.

My doctor prescribed be Evalil for anxiety and to help me sleep at night. I just started taking it but read up on it. It says the number one side effect is weight gain. I absolutely do not want to gain weight so I am going to go back to the doctor and tell him this. 
I lost 30 pounds a few years back and am at a weight I want to be. Losing 30 pounds took forever and was hard work and do not want to gain it back. 
Will my doctor look into something else? Or will I look ridiculous going in and saying this? I know most anti depressants/anxiety meds probably cause weight gain but some less than others.