Are there any substances, medications, or herbs I can take to get rid of nervousness?

Yes. I recommend seeking a professional consultation. There are many options available but they are patient specific and much too complex to address in this forum.
They help. There are lots of herbs like chamomile [peter rabbit got it after the briar patch], as well as micronutrients, body work, yoga, meditation, tai chi, mindfulness. A compassionate professional eval is the first place to start.