Agree with everyone else. It’s embarrassing, but it’s not like you have to show them what’s going on. Just tell them you need to see a doctor for it.

If you’re really so uncomfortable telling them about this that you can’t bring yourself to do it, then you could try telling them “I need to see a doctor. It’s embarrassing, I don’t want to discuss it, I just need to make an appointment. I’ll handle the scheduling, I just need to know my insurance info* and a ride to the office”

*Or however that works where you are.

If you can reasonably do it, you may just be able to call and schedule it without their help.