Hi thanks for the query.
The complaints of low back pain
some times is related to wear and tear in the spine. The swelling of the entire right leg along with ankle and foot is of concern and you should visit local orthopaedic surgeon
. Since you had not mentioned about any cardiac ailments in the past i could not compare it to heart related problem. Gain in weight could not be explained with available details you had given you. It is better to visit local physician also.