First RE appointment

I have my first RE appointment tomorrow and I am nervous. I did a few clomid cycles with my ObGyn, ovulated 2x on 100mg and my 3rd cycle on 100mg the ObGyn said my progesterone response wasn't good and referred to me a RE. I am really hoping a RE is able to help.. What can I expect? And do I have to go through a whole cycle of testing before they will do anything? My cycles can skip months and I am worried I won't get any sort of treatment for awhile due to all the testing. Any advice would be welcome!