How should I go about endo screening

I’ll be 18 in less than a month and have suspected I have endo since I was 14. I have asked if there is a way to test for it and always been told the only way to know for sure is exploratory surgery. I have recently been told by a friend that a vaginal ultrasound could show it. I have been told that I’m too young and it would be too painful and/or traumatic for me but I truly don’t think that would be the case. Do y’all think this could be a good idea and if so how do I go about presenting my case to my gyno?