Thanks for the query.
As you are on birth control there is less possibility for pregnancy
Sometimes bowel movements can also be interpreted as fetal movements.
As all your tests are negative the chance of pregnancy is less.
If you want you can once go for repeat ultrasound
Which will rule out the possibility of pregnancy.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429