Don't give up on the watch just yet!
When I bought a stainless Oyster/Rolex watch I found it so heavy, but now I don't even notice it at all. I even wear it to bed if I staying/visiting a 'dodgy' area!
Your body will soon adjust to the new weight, so if you like the watch just keep on wearing it and all will be well eventually.
If not, there is always ebay.......