Hi Sara and welcome.

I've had anxiety as well, particularly in crowded areas like the grocery store.

Some non-medicinal things I have found helpful are:

Mindfulness meditation. There are a lot of useful books on the topic, Wherever You Go, There You Are by Jon Kabat-Zinn being a classic. Meditation classes may be available in your area, I found a non-credit class at a local community college.

Gentle yoga. I would suggest a studio that combines traditional meditative practice with the posture practice.

Massage therapy.

Three month probably seems like a long time, but in the TBI/PCS world your injury is relatively recent, and while all TBIs are different continued improvement is likely.

Related to your motion sickness feeling, I still have occasional vertigo after 3+ years, but it is relatively minor and I have learned to make adjustments.

Best to you as you continue your recovery.