Host parents opened my mail

(23F Au Pair in Germany)

I have found 2 opened letters that were addressed to me, they were both invoices from the doctor’s office where I had an appointment (regarding my sexual health, so it’s very personal). One of the letters has a full breakdown of the services I received.

They clearly had my name on them and I never received them, I just found them open on the kitchen counter.

Obviously my host parents would need to know the costs for the insurance - but I feel a little violated that they opened mail of a very personal nature without consulting me first? Am I over reacting? Is it perhaps a cultural difference that I wasn’t aware of???