I just got new bed sheets and have rash/hives/bumps all over my body, why?

Bedsheet rash. Dyed new sheets or clothing or permanent press textiles that are not adequately washed prior to use can cause rashes due to contact sensitivity to dyes or formaldehyde/formaldehyde releasers in permanent press clothing. Always best to wash new clothing multiple times before wearing if you are sensitive to these things. Patch testing could delineate what your exact allergy is if you have one.