If no endo picked up on ultrasound?

Hi everyone. Long time follower but first time poster.

I’m booked in to have my laparoscopy on 12 April after having symptoms of endo for 20 years. I’ve always just been told that I had IBS or painful periods, etc so haven’t done anything because thought I was being dramatic. In recent years it has been getting worse and worse (I’m 35 now).

I’m starting to get worried now that I will go in for my lap and there will be nothing and it will all be in my head.

Someone (not a doctor or my specialist) told me the other day that if nothing comes up on your ultrasounds you won’t have endo. All my ultrasounds I’ve had over my life and recently have come back with nothing.

I’m just wondering if anyone has had the experience where ultrasounds have turned up nothing but on laparoscopy they found endo and can you have severe stage 3 or 4 endo without anything showing on an ultrasound?

Thank you in advance 🙂