How Safe Is Using Tampons With Endometriosis Condition?

Hi, I am a 15 year old female and I ve just recently used tampons for the first time. My mother has concerns about me being too young. And wearing them while swimming. We believe I have endometriosis as well and she feels that I should not wear them if I do indeed have this condition. I take them out at appropriate times and keep my hands clean. So there s no issues there. But can you please tell me if she is right about any of these things?