Sucking his dick

When do I stop sucking his dick? When I was with my ex I was sucking it & when he started coming I was gonna stop but he told me to keep going till he was done & he seemed to enjoy it a lot but every other guy talks about how it hurts but when we had sex he didn't want me to keep going I'm so confused😂🤦🏻 idk what to do I wanna make my man feel good but idk when exactly to stop/: any tips on that??