the possible causes for your pains are,
-gastritis-which is common in pregnancy
associated with regurgitation of food can cause symptoms like this,
-as baby in breach position kicking movements may be noticed like this,
-usually uterine contraction start from fundus of uterus
so that may be reason for it,
anyhow as your doctors examined and told nothing to worry,
you practice measures like taking antacids, lying in left lateral position, keeping two pillows behind head etc. if symptoms becomes severe better to visit your doctor early.