What size mice is considered too big for my snake?

My ball python is about 3 months old and about 18 inches long. he won't eat f/t mice and he hasn't eaten in 4 weeks. To me he's looking a bit underweight. I was wondering if an adult mouse is going to be too big for him. When do bp's start eating adult mice? I have a picture but I don't know how to upload it to this post/:

can someone tell me how yo upload photos? sorry im new to this

http://tapatalk.imageshack.com/v2/14...69cf0bcbbf.jpg

http://tapatalk.imageshack.com/v2/14...9352dfbcf1.jpg

Are they about the same width? It's hard to tell from the picture.

Edit: Nvm...that second picture is pretty good. IMO that mouse looks too big...

thanks. do you know when ill be able to feed him adult mice? where i live its hard to get smaller mice that arent frozen

There's really no way to know that...they tend to grow at different rates. You could probably swing the next size down from that. I'm sure he could probably eat that but I'd be feeding more like every 10 days as opposed to every 5-7 days like you would with a smaller prey. Your guy is pretty tiny though, I'd try a few feedings with smaller sizes and see how well he takes them.

I have one that is approximately three months old, and he is eating rat pups which are probably the approximate size of an adult mouse :gj:

My snake is about that size and I feed it "hoppers" Thats what the pet store calls them anyway.

thanks guys. do you know if petco sells live feeder mice? the nearest petco is a 35 minute drive