why does he have a melon rind on his head?

too much nip and el natural cat food

JP - you need to get checked by your doctor. Heart attacks can cause
pains in all kinds of places, an arm, the jaw, your back, or even just
feel like a really serious case of indigestion. You could have had a
minor gallbladder attack (if it was on the upper right side) too, but
you do need to have it checked out. Make sure your blood pressure is
good, whoever recommended that was right. This is nothing to fool with.
There are even silent heart attacks that people have and never know,
until they may have an EKG and find out they have had a heart attack or
even more than one. Don't fool around with this and get it checked out.
You are young, but I have heard of young guys in their late 20s having a
heart attack, it does happen. Never put off getting something like this
checked out, you might not get a second chance. Take care of yourself.

I think the cat should get off the nip. It could be a problem in future.

Already has caused problems, the future is now...he tried chasing snow
flakes through the window this past winter, runs into the door when
squirls are in the yard (that is when he needs his protective helmet the
most). Poor fella, feel sorry for him when he slams his head into the
door