First, I am sorry. High FHS is devastating to hear.

I am totally there with you, my highest being 40, down to about 23 now.
OK, There are all different levels of "High" so I'm not sure what you are at now. Some quick answers: Do they fluctuate, yes but most Dr. say your worst one is where they set you as it is indicative. Can you lower it, yes, but it won't necessary help. Do people with high FSH get pregnant, yes, they can. There is a great support board for ladies like "us with high FHS, look up:
https://www.network54.com/Forum/209394/
They have been very very helpful for me! They have a lot of info and are a very aware bunch, much more "medical" than this board, which is also very helpful, which is why I am on both!

A lot of the women are at one clinic but a bunch of us are not, so no worries! As far as lowering it: Acupuncture and herbs have really helped me, but again, lowering it really may not help.
The only time, it seems, that you can have a false high FSH reading is if you just came off birth control pills. You should also be tested on the third day of your cycle for the most accurate number.
The FSH
itself is not the problem, it's just the hormone that your body is putting out to try to get your ovaries to keep putting out eggs each month. So, what you need to know, if they have not told you already is:
If you are still ovulating
How high exactly your FSH is
How your ovary size is
And your ovarian reserve.
Now, warning: most RE dr are NOT friendly to high levels. I was told there was no hope and to try donor eggs. Personally, my husband and I chose to find someone who would work with us and we set a clear amount of time we were willing to try for, after that we are moving onto adoption.
So, there is hope, please find out all you can and good luck!

Hope all this is helpful,

Sara H.