As the food pipe- stomach junction is slightly immature as this age small children have got a tendency to vomit. What you can do is after giving breastfeed burp the child for at least 15 to 20 minutes. Also keep the head of the child at slightly higher plane compared to the lower part of the body. Make sure that the top milk you are giving should be given in a clean utensil with spoon (avoid bottle feeding). the use of colimax again and again will lead to constipation. Burping the child adequately so that he burps two to three times before going to sleep decreases the chances of gas and thus decreasing the chances of vomiting. If vomiting still persist after doing above mentioned steps please meet a doctor to rule out infection or any other cause of vomiting.