Hello from JustAnswer.
There are many possible causes of red, blotchy skin, but the worsening that occurs during and after exercise is because of flushing of the skin, which will make any other cause of skin redness more pronounced.
As for the baseline redness, in an otherwise healthy young adult, it is more often a benign issue, such as excessive dryness of the skin or a chronic reaction to skin care products. It is also possible that the skin can be red because of systemic reactions to substances taken internally, but it would usually occur less often. There are some medical conditions that can affect redness of the skin, such as labile blood pressure and certain hormonal conditions, such as thyroid disease.
You are also correct that the fairness of your skin will make the redness more apparent, regardless of the cause of the redness.
Based on statistical probability, it would be reasonable for the next step to be interventions to help hydrate the skin, such as regular use of a skin moisturizer and the use of mild soaps without any scents to limit the dryness of the skin.
If you can attach a picture of the redness of the skin, then I may be able to make more comment.