Saberwriter makes good points, so I'll address another way to address your concerns.
Your character has anxiety, but there can be a lot of variety in that. At any one moment it could be a general feeling of unease, twinge of fear, distracting panic, or mind-numbing inability to focus on anything else.
If you vary the reactions, their levels, and most importantly the words you use, it will address your concerns.
The Emotion Thesaurus (good book) lists a lot of reactions. Some are:
- touching the face
- shaking of various limbs
- twiddling thumbs, watch, rings, etc
- swallowing and shifting feeling hot or cold dizziness
- tingling in limbs
- chest tightening
- difficulty breathing
- worrying about worst-case scenarios
- heart palpitations
Many of the above can be found in medical descriptions of panic disorders.
As long as the reactions you focus on shift each time you're fine. It helps if you focus showing the physical rather than mental response (which will always be fear). Dizziness and breathing one time, heart racing and sweating the next, nausea and him noticing his limbs shaking another.
Once you've varied the reactions focused on, you can then vary the exact way to present the symptoms you choose. A quick search will turn up a lot of ways to describe the feeling of being nauseated (bad taste in mouth, stomach cramping, saliva in mouth, rapid swallowing, sensitivity to smell, etc).
Then you can put some "pretty" spins on it by varying phrasing. Similes and metaphors will help a ton here - they are usually more "literary" than adjectives. He can feel the acid churning in his stomach, his gut was filled with lava, his insides turned to liquid doubt, his anxiety turned the burrito he had eaten for lunch into molten lead, he had to swallow to not retch all over the table. Fun stuff.