What Causes Irregular Spotting And Hard Feeling In Stomach?

I am a 24 yr old mother of 3 (All c-sections). Last c-section had a tubal ligation (4yrs ago). I have been spotting irregularly for several months now. For the past 9 days I have been feeling kicking and actual movement in my abdomen. I went to the hospital 4 days ago and the blood test came back less than 1. The movement when I place my hand over belly and can be seen. They told me that it's my bowels however, remember that I have had 3 successful pregnancies and know what I am experiencing. Finally, my stomach is hard and round and is obviously growing. I am not a large woman (125p, 5'6''). Any thoughts?