First appointment at the fertility clinic

Hi everyone, my first post on here so bare with with!! 
-long story short, I got diagnosed with Polyscisitic ovaries syndrome when I was 15, and last May I had keyhole surgery and got diagnosed with servere endometriosis, I will be 23 this April and me and my partner have been trying for a baby for 3 years. Since the operation in May we still have had zero luck, and I'm due to go to my first appointment at the fertility clinic and I'm really nervous and unsure as to what will happen and what to expect? 
Can anyone reassure me or tell me what to expect? 
Thanks! 🙈xxx