Many pharmaceuticals (over the counter and prescription) are bonded with binders that can cause lupus patients problems.
As an example in Alison's post above of non-active ingredients in Nytol : if the patient is lactose intolerant ... Nytol would then be a no go.
The fennel tea itself should not cause a problem - anti-spasmotic anti-bacterial detoxing properties. Was it certified organic - without pesticides? If not, the fennel could have been chemically treated prior to drying for use as tea.
Always read labels. Know as best as is possible what you are putting into and onto your body.
Flare up triggers are not always possible to avoid. Sometimes no trigger is required as lupus does what it does.
You state you are breathless when NOT in flare up. Check that your BP is not too low - if low contact your doctor. If you are urinating more frequently than normal contact your doctor. Any other symptoms contact your doctor.
Definitely speak to your doctor about your breathlessness as it could be a number of issues. Best to be safe.
Inform the doctor of your resistance of taking Azathioprine and ask for better options. Honest communication with your doctor is the only way to gain the best solution for you.
I hope you feel better soon.