Rice Cereal. What happened???

Ok so when I went to the doctors for Connors 4 month check up the doctor told us we could try giving him rice cereal to help with the acid reflux. So when Connor turned 4 months on Christmas day I gave it a try. I added it to my breastmilk and tried to give it to him with a spoon. Well that didn’t go to well because he just spit it out so then I added it to the bottle…..I only did 1 teaspoon to 3 oz of breastmilk, so it wasn’t much at all. To make a long story short we did this about 6 times and never saw anything positive or negative happen so we stopped. For the last week or so Connor has been chewing on his tongue so we thought we might try to feed him with a spoon again to see if he would and he did (it was the cutest thing ever to see him eat food) Well anyways this was at 7:30pm and for some reason he was up til 9 just laughing and playing (he usually goes down at 7:30) so then I tried again to put him to bed and nursed him at 9. We both went to bed and about an hour later something woke me up. I looked over at Connor and he was still sleeping but I was worried because I thought I heard him make a noise. So I reached over to touch him and I noticed he was really wet so I turned up the lights and notice he had spit up. I cleaned it off his face all the while he was still sleeping and then he started to fuss a little so I went to pick him up to see if he needed to burp and thats when he vomitted all over the place and started choking on it. So this continued every 30 minutes he would wake up and cry out then vomit…..I have never seen a baby vomit but its like when us as adults have the dry heaves…..his back would acrch and blah…I was so scared to death. Finally when he was asleep for more then 30 minutes with out vomiting I was scared he would get dehydrated so I decided I would try to feed him. For the rest of the night he was fine I just laid with him in bed and let him nurse as much as he wanted. Then this morning he was fine but his first diaper was so watery and there was a lot of it and it stunk. He has been eating just fine all day and had one more diaper that was watery and stinky. So my question is did the rice cereal do this? Anyone else have this happen?