Hi, thanks for writing to HCM.
From the description , I feel the swelling of your legs is due to PHYSIOLOGICAL DEPENDENT OEDEMA which usually occurs after prolonged sitting, standing or lengthy travel. This will subside with simple elevation of the limb.
On the other hand, Cellulitis
usually develops as a result of an infective process in the limb. So the limb will feel warm, red, tense and tender with associated high temparature. As you don't have all these symptoms, cellulitis can be ruled out.
Hope this information is helpful. Good day