What could this pinkish / red blotchy hive rash covering my chest, stomach, neck, sides & back be?

Hard to tell: It is difficult enough to find a cause for a skin rash even by examination, it is nearly impossible to even make a guess without direct examination. See your doctor or a dermatologist.

Hives: If you have hives, the rash should be itchy and it should be dynamic (each spot tends to move or disappear before being replaced by another spot). First or second line antihistamines are a good first step if you suspect hives. If this is recurring or persisting for more than a week, consider a virtual consult to discuss potential causes and the necessary work up.