don't hate on bananas! we love them at our house, especially now when all other fruit is SOOO expensive due to being off season. (i saw a bag of plain-jane apples for almost $6 yesterday. UGH!) one a day, i don't know - my son is 4 and does fine with one per day. you really should just ask his pediatrician if you're concerned. don't ever go just by someone's opinion, and the internet lol. but babies get constipated, it happens. i'm sorry that it happened to you.
but as far as spitting out other fruits - i would cut back on bananas and keep offering them, just based on that. keep offering it, don't give in and give him somerthing else (until next meal at least). if you get him used to "this is what we're having" he will fight it less. babies have to get used to different textures and flavors. if you assume that "he tried it once and it ended up on the floor" means he won't eat it, and never offer it again, you'll just ensure he never gets to like that item. keep giving them to him! good luck!