Tried to break up with my bf, now second thoughts

So my boyfriend and I have been dating for about four years. I recently tried talking to him about me not being happy in our relationship and that I was starting to get bored.He pretty much blew it off and nothing changed. I had also tried suggesting that we move in together and he seemed to be really hesitant about that which really bothered me because I am really looking for a new excitement in our relationship. So after all of this I began to rethink our relationship and started to distance myself from him until I got to the point that I wanted to break up. Earlier today I was dead set on breaking up and went over to his house to do so.
We talked for like two hours about all of this and he is now promising that things will change and that it will be a permanent change and that hes really sorry and so on. Also, another reason that I wanted to break up was because I feel that he is really immature about things such as he hates everything and everyone and thinks he is better than them. Also he can act really dumb when he is drunk and I cannot stand being around him like this. Because of those things, I have been doubting if I can see us being together forever.

Today we settled on that I would rethink my decision and get back to him. I just do not know if I should get back with him because I feel like things would only change temporarily and I do not think that his immature actions would ever change. Also, another thing that is making this all complicated is that I have been talking to someone else and have begun to develop feelings for them. I know that this should not be the case as I would need time to heal from this breakup and it would be a rebound, but at the same time I cannot change how I feel for this person. I would not date this person for a while but I just feel that the fact that I can even have these feelings shows a huge weakness in my relationship.

Should I keep with my original plans and break up or should I let him try to fix things, even though I already gave him a few changes to fix things before?

It seems like although you're indecisive about what is best it would ultimately and probably be better for you and both for him as well if you just ended the relationship.
You said you aren't happy with the relationship and remarked upon several aspects which you didn't like about him and how he acts. You said that he acts immature at times and nothing much has changed and you doubt that it will. You should ask yourself if you remain in this relationship will it be worth continuing feeling in such an "unfulfilled" way?
It's possible the connection between you and your boyfriend has dwindled and you said how you have even now developed feelings for another man. You've clearly seemed to connect with this other man if you have gained feelings for him. So even if you aren't physically cheating on your boyfriend you are not emotionally investing and devoting everything that you can into your current relationship. If you aren't happy with how things are it would be more fair to your boyfriend, and especially if you are interested in someone else, to just end it.

Remember its your life and if ur not happy? Then its time to move on. imo I mean, u tried to make it work and u did tell him how u felt but nthn changed. Hey, try takin time off with each other.