Some follistim/follicle questions...

Okay, so I've been on follistim for 4 days now for IVF and feeling a little emotional. :o They said at my last u/s that my follicles were still small, but they haven't told me how many I have yet. I go back in tomorrow morning for another follow-up. And they started me on 200 units and yesterday it went down to 150.
Here's my question, what size are the follicles supposed to be at this point, almost half way through the follistim? And, what size do they need to be for the retrieval? I'm concerned that they lowered my dosage even when my follicles are still small. Is it b/c of my LH or estrogen levels? :confused:

If anyone has any information, I would love to hear about it! Thank you!