Quick unwanted weight gain...help!!!?

I see a lot of leg work. You could be gaining a lot of muscle there depending on the intensity of the work out. It happened to a friend of mine she was always doing high intensity leg work like stairs and biking. You say you lifted some quite heavy weights as well? I do moderate weights for tone and endurance heavy weights are for strength both give muscle, but strength builds more bulk. You could also be retaining water as well so the weight could be water weight.