I hope your plant is doing better now.It sounds like your plant was overwatered or allowed to sit in water for too long. It wants the top 2" of soil to dry out before watering again. A bright spot out of direct sunlight is best. Take a look here.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.