Catching cum?

So my Fiancé wants me to catch his cum in my mouth but I can't.. Its like I gag every time and some times throw up.. My question is has this ever happened to you and if so how did you over come the taste? Any tips or tricks.

Dont know if this is the right group no negative responses if this isnt, just please point me in the right direction.

Thank you.

Edit: Thank you all for your help... I will be trying these tips 😊