What Causes Soreness In Abdomen,spotting And Weight Gain?

I am a 37 year old female with 3 children. Approximately 3 days ago I started having some spotting (not real dark blood, but it is not my period).I also in the last 3 months have gained about 20 pounds. I haven t changed my eating habits, in fact I have been trying to lose weight by drinking protein shakes and eating more fruit and veggies. I also have had some soreness around my belly button?