I Have My Tubes Tied For 3 Years Bout To

I have my tubes tied for 3 years bout to be 4 year in Jan.. I started my period four days ago and I'm still on it. Toke a pregnancy test last Sunday and yesterday morning I started feeling little ball knotting up on my right lower side and when I would put my hand on ot . it would disappear or move somewhere else can you tell me what you think it might be???