My experiences were all similar. There were questions about my history, family history and the events that led me to seek treatment. They also wanted to know about current meds and my history with meds.
I agree with FearLess. They are there to help you and there's nothing wrong you can say. They have heard it all and just need an accurate picture to work from.
Keep in mind you can interview your provider as well. Write down all of your questions and don't be afraid to ask for clarification on anything that you need more information on.
Good luck to you and I applaud you for taking steps to get help for your health. I understand the nerves, but it can be a huge relief to start on a new treatment plan. Try to spend time looking at it as the start of feeling more supported.