How do you answer a guy when he says prove that you miss me?

tell him when you two are apart your heart weaps.

Answer

It's difficult to prove to someone that you miss them if you cannot see them in person but you can tell him that you think about him all the time, that you cannot wait to see him again, that your life is not the same without him in it, that some days you miss him so much that your heart aches and you are filled with sadness. Then tell him you'll prove how much you missed him when you see him again. :-)