Two to three weeks is usually not enough time for them to become totally secure. He will likely improve with time as he gets used to everything and feels secure when you step away from him etc. I find that sometimes it takes months for them to reach that level of security...it just depends on the child. That said, only YOU know how much you can take and how much time you are willing to give it. Personally, I would give it at least a month, but if you can't you can't. Good luck!