Why is he bothered about my sex life

So we were having a conversation on the phone about people saying we wanted to fuck each other and I said I wouldent your like a brother to me and he said I wouldent anyways I heard you’ve got a disease meaning an std I said I’ve got the test results I’ll show you I don’t and he said what so you’ve never fucked these guys in a shocked voice and I said no why is he so bothered and what is he trying to say