How Do I Tell my Boyfriend to get Checked?

Sooo... this past week i had noticed some weird yellow discharge in my boyfriends underwear... i never addressed him because i didn’t know if it was a stain or old & i had no symptoms.. i tried to convince myself it wasn’t what it actually was. So i took pride in myself went to my OB and had gonnorea ... i get checked regularly so i know it’s from him.. i just don’t know how to tell him he’s got it without him taking offensive or being upset