Plantar fasciitis can occur bi-laterally, but generally it will just be in one foot. There could be a number of things that contribute to that. The biomechanics of the hips and knees play a role in how effectively the foot is being used.
Other factors that may be relevant include:
Early treatment is ideal for resolving plantar fasciitis. After the first two weeks of plantar facia pain, the issue starts to become sub-acute or chronic and it's so much harder to get on top of it. There is also the risk that degenerative changes will occur, which cannot be treated. Ideally we would want to have it at least examined to determine what is going on before this happens.
Icing and massage can be combined. We can use certain techniques like a patty roller, a concave device which you store in the freezer. Every half hour, especially if you are sitting at a desk throughout the day, roll the foot backwards and forwards over the roller for a couple of minutes at a time. If you don't have access to one of those, use a plastic bottle filled with water. Once it is frozen, use to as a roller for your foot. That soft tissue technique will start to break things up, loosen up plantar fascia and start to help.