Your baby is getting smarter and very curious about everything. That's why you can't keep your bb at your breast continuously for say 15min.
You don't need to provide cereal so early. Better wait until at least 5.5 mth old. Back to basic, if there're 6 wet diapers a day your baby should be fine. If not, try to keep your baby suck for say 8-10 min each meal (though it may not be easy). 3 hours in between meals should be fine, actually mine was 3.5-4 hours when she was 4 mths old.
Dr said that if nostril is blocked it's hard for baby to suck. But sorry I dont know how to tackle this.