I wouldn't worry too much, nexis. Tests can vary a lot...mine changed so much, I was convinced something was wrong. But so far, so good! Are they going to test your hormone levels? If they do a beta, your numbers should be at least doubling every 48 hours, to show that the pregnancy is progressing. It may also be worth asking about getting some progesterone supplements...such as cyclogest. It can be a problem with pcos, and without progesterone the pregnancy will not be supported. so maybe worth an ask?
Aein, I would go for it...what do you have to lose? It's a good procedure. Will you be having it funded on the nhs? I'm sure you'd rather have something slightly more invasive, but know that you're moving in the right direction? As they've said, you have had a lot of clomid cycles now with no luck....