Your corn looks like a young one, so yeah, a pinky mouse every 7 days will do.The person I bought it fromm says to feed it a pinkie once a week.
You'll see the signs: lethargy, not feeding, or something else doesn't look right...you'll know it when you see it...Don't freak out if it doesn't eat though. Snakes do skip meals for no apparent reason. Skipping a meal or two is no big deal for a snake...but when this lasts several months, then it's time to find out what the problem is, sometimes a perfectly healthy snake just doesn't like what you're offering (usually not a problem with any corn, unless you're offering crickets) or how you're offering it...Frequently skipped meals are generally a sign of an error in the setup: temps/humidity too high/low, feeling insecure due to lack of hides or being kept in high traffic areas (remember, a snake cannot use it's mouth, it's only defensive weapon, when that defensive weapon is full of rat)...But How do I know if its getting sick?
Just make sure it always has clean water...I almost never see my snakes drink, but trust me, they do...A well-hydrated snake's skin rests nice and tight on the body...a dehydrated snake will have wrinkly skin...Or getting water?
The snake probably will turn down food, colors will appear dull, eyes will look cloudy, and the skin may appear wrinkly due to the old skin being in the process of detaching itself from the new layer of skin underneath...a snake with cloudy eyes is considered "in blue"...when your snake is in blue, just bump up the humidity which aids in a perfect shed...at some point, the eyes will go clear, and you should see shed skin in a day or two...Or ready to shed?
There are several methods, the most accurate method is to "probe" a snake. Basically, these are metal probes that you lubricate then "gently" insert them in the vent and gently push in towards the tail, then you count by the number of belly scutes (scales) that the probe is in...the probe will go in deeper for males than with females...Male or Female?