I need advice how do I tell my bf I can't give him oral because every time I do it I get really sick

  Okay so two weeks ago I gave him oral and th next day I woke up with a terrible sore throat and these painful sore type things all over my mouth and down my throat I got scared it was an STD so I went to the doctor and he said it was strep throat and bad acid reflux so I figured it had nothing to do with my bf but now the same exact thing happened I woke up with a bad sore throat and sore type things and it's really painful and scares me so I can't give him oral without getting really sick how should I tell him I can't do it without him getting mad ?