zyprexa weight gain-what to do?

I've gain about 50 pds on zyprexa and now I'm prediabetic. I tried coming off of it but its not possible. What antipsychotic should I switch to that wouldn't cause insomnia or anxiety?

Yeah, I was obese and put on about 5 stone when I was 26 when this $#%^ first started to happen, I found out later what it is, though the treatment for so-called mental illness is an obvious sham, the best thing to do is bin them now and start educating yourself as too what really going on!.