Birth control question

Ashley
What's the best birth control that doesn't tend to cause weight gain? I'd rather a IUD i think. Is it hard/expensive to get a copper IUD? I was on Orthocyclen back when I was 16 and I got faaaattt! lol
I'm 30 and my husband is 47. He has a 22 year old son and doesn't want anymore kids. I am on methadone atm anyway.