Depression Medications

I am currently on 30 mg a day of Lexapro and 45 mg a day of Remeron.  I was on 20 mg a day of Lexapro only, which worked great at first but after a couple of years on this dose, it just wasn't cutting it anymore.  So my psychiatrist added 30 mg a day of Remeron, which helped me sleep, but I started waking up in the middle of the night, so he upped it to 45.  Since I was still feeling somewhat depressed he also, on my request, upped the Lexapro to 30 mg a day.  My problem is that I am really hungry on these drugs and have put on close to 30 pounds since August.  It has been difficult for me to lose weight even with regular exercise since I am so hungry.  He told me that I could try Topamax instead of the Remeron to help me sleep (I haven't switched over yet though), but I have been researching Topamax, and the side effects scare me, especially vision and cognitive problems.  I've tried other sleep meds--Rozarem, Ambien, etc., but the Rozarem didn't work and the Ambien gave me headaches.  So I am not sure what to do.  I hate the thought of either having cognitive and/or vision problems or being fat, or else taking neither the Remeron or the Topamax and being unable to sleep. Any thoughts would be appreciated.