I had itchiness and rashes on my buttocks area that left skin pigmentation and now it's spreading to my back, both the rash & the itch. what can i do?

Rash: The rash you describe may not necessarily be related to your other complaints, each one can be dealt with individually based on symptom control. The rash sounds like a fungal infection,need to be seen for a diagnosis, it's localization could be a drug reaction but unlikely to loratadine. Flatulence could be diet related. A visit to you PCP is required, for best care resolve issues promptly