Sonohysterogram - can it detect blocked fallopian tubes? How do you check if it was a spasm or a real block?

I am attending a fertility clinic in order to find out why I am not getting pregnant. I am 42 and have been pregnant 4 times. Last time was when I was 36. The baby did not connect to the wall correctly and was slowly dying from lack of food and oxygen. The hospital "took" the baby as my life was apparently in danger. So now, I have had two ultrasounds - stomach and the "inner" ultrasound, and blood work twice. And today, I 'failed" the sono test. Apparently the tubes would not allow the saline in. The doctor said it might be a spasm blocking the tubes, or they are blocked. I do have endometriosis and have had it since I was 16 years old. It never stopped me from getting pregnant before. So since the saline "fell out of me" instead of going where it was supposed to, and my follow up appointment is not until July. I thought I would ask what people know about this test, and if anyone with a supposed "block", did not really have a block. I did see that 15% is the ratio of false determinations for Sono's. Appreciate any and all positive commentary.