From what you have described.I presume you might be having one of the following as mottling is the key feature in all of these conditions:
3.Cutis Marmorata Telangiectasia
Since you have specified that all your blood investigations are normal.I suspect that you are having erythema ab igne. It is caused because of keeping the laptop on the thighs and legs for long hours.
It can be reversed by simply by avoiding keeping the laptop on lap directly.Anyway since i have not seen you, i suggest that ask your dermatologist
to rule out the these probabilities by relevant history,physical examinations and investigations.