There are two kinds of rashes on your back One which are raised bumps could be due to allergy, drugs etc. Since it is not very clear cannot comment more on that. The white rash could be due to past allergy or fungus. Is the rash itchy, a detailed history and examination is required.
Next Steps
Send more clear pics of the lesions. Go for in clinic consultation if possible or else online consultation.
Health Tips
Take some anti allergic tab for itching