Asking about STDs and STIs

How can u ask a guy if he had any diseases and who his last sexual partner was when the two of you are both in high school and don't want to make this person feel like u think they're basically a hoe? I am pretty positive he doesn't just go around having sex and I believe I know who his last sexual partner is but I have developed cold symptoms which I think are for drainage but I just want to be sure..