Most Helpful Guy
I completely understand what you're going through, I still thought about my ex girlfriend after we broke up for a couple of months. I asked myself the same exact questions your asking yourself now. It's not wrong to think of your ex, because you created memories together. Whether they're happy or sad memories, they're still memories that made an input on you. Instead of thinking like it's a bad thing, I think that you should learn from it. Use though memories to help you grow as a person and become stronger as person as well. Like when you're trying to find someone else, you could have better judgment on who to look out for and who to avoid. Thinking about your ex could reveal that maybe what you thought you liked in a guy isn't what you like at all. However, if you're like me and thinking about your ex and still have feelings for that person, I can tell you that it'll go away, but it'll take time. I recommend that you do whatever it takes to get your mind off of it, like hanging out with friends or going on adventures, trying new things, etc. It's completely normal that you still think of your ex, many people still do and some never stop. the first thing I do recommend that you do is to stop getting irritated over it, because it just means your acknowledging it. I hope this was helpful, and of course this is just my opinion, so you don't have to listen to me.
Most Helpful Girl
Was he part of your everyday life for more than a month or two? You can't just "get over" and forget everything instantaneously. It will take time, and moving forward by making new memories. Make plans as often as you can with other people who don't know or talk to him, or his new girlfriend. Distractions!