Given that you have Fibro, and it is thought that upwords of 95% of people with Fibro have Lyme, and given you were bitten recently by a tick and have rashes, then I would say it is possible that you have Lyme. A Lyme-Literate doctor is the best person to confirm the diagnosis if you never had the "classic" bull's eye rash...Lyme tests may or may not be helpful...and tests are not required for diagnosis if the clinical picture fits. Furthermore, if the antibiotics are making the rash go away, then I'd say it is more likely that the rash is from some infection than from poison ivy (poison ivy rash is actually an allergic reaction and thus won't respond typically to antibiotics). The hydrocortisone cream may help an allergic rash, but won't help an infection-related rash (other than possibly with itching).
I hope this helps...good luck,
Chronic Lyme Disease, Chronic Bartonella (clinical dx only), Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, chronic Lymphopenia, etc.; G-Tube; Currently weaning off TPN.
Meds: Pulmicort, IV Doxycycline, Heparin (to flush PICC line), Claritin, Singulair, Domperidone, Colloidal Silver (topically & nasally), probiotics, Liver support herbs, Ailanthus, digestive enzymes, homeopathy.