1. Don't make the baby lie on her back immediately after the feeds. The choking may be due to the milk in the stomach refluxing backwards into the food pipe and coming up to the throat causing some amount of choking . After a feed burp the baby and keep him upright in the burping position for another 5 to 7 minutes even after she has burped . Thereafter dont make her lie down flat on the bed , instead put a small pillow under her head and shoulders so that the upper part is about 30 deg elevated and turn her on to her right . This prevents backward flow of milk and also enables the rapid transit of milk to the intestines . 3. In general you can feed breast milk with baby  lying down ( but not bottle milk ) but as you say your baby chokes while lying down , I would suggest you don't do that.  After feeding follow the instructions about placement of the baby as in the previous paragraph