I Have A Boyfriend Who I've Kissed Maybe 10 Times,

I have a boyfriend who I've kissed maybe 10 times, and we are learning about hiv at school. I don't think he's ever had sores by his mouth.. but he has acne and stuff I guess on his face.. scared one maybe couldve bled and got into my mouth? anyway I can know or am I just paranoid and it would take quite a bit of blood?