I have been taking Remeron for two weeks and have gained 15 pound...

Hi. I have been taking remeron for about 6 weeks with 20mg/day lexepro. For the first week I took 15 mg and it put me out like a light. The reason my doctor prescribed it was because I was severly depressed and lexepro wasn't helping and I was sleeping from 10-14 hours but waking up every hour. Now I have to take the remeron by 7 or 8pm so that I will wake up to go to work. It puts me out for a good 12 hours. My depression has lifted and my appetite returned with a vengeance, like I see most people have. I've gained about 10 pounds and altho I'm enjoying food again, it's just too much weight gain and that depresses me. I feel like I just blew up before my eyes. Not sure what to do because I'm so glad the depression is gone and I'm enjoying people and work again.

Why do we gain so much weight on remeron?