Yes, that’s normal to feel that way, especially starting out.
Since you’re so close to your first session of ERP with a professional, I’d suggest looking at your daily and nightly schedule—if you have one—and see areas where you can improve. If you don’t have a daily and nightly schedule, start planning one. Being really unorganized and not on a routine can make mental illnesses and stress worse. Also look at when you go to bed, how much hours of sleep you’re getting and then when you wake up. It’s suggested to have 7 to 8 hours of sleep every day for best cognitive functioning.
Next, I would start practicing mindfulness, and that also includes reading up on how to start. Thich Nhat Hanh is amazing; he was a Zen Buddhist teacher that has a lot of books and guided meditations online. Meditation apps like Insight Timer or Calm will be of great use to you. Get at least 30 minutes of exercise per day, limit your internet and device usage, and get used to going outside, even in cold days! Go for a walk on your own, with loved ones, or take your dog out for a good walk—if you have a dog, they’ll love it too.
The key to getting better is to excepting uncertainty and letting your thoughts be present without fighting or arguing with them it needs to be there and you need to not engage with your OCD. Also do not alter your behavior for OCD in any way, shape, or form because if you give OCD an inch it will take 20 feet.