Is it normal not to forget your ex?

so one day my friend told me that her friend thought i was cute, and so i met the guy, at first i wasn't that interested, i really didn't care. so he asked me out and i said yeah sure, ill give it a try, he is two years older than me, he really liked me, he cared what i had to say, and listen. so we went out for a month or so and by then we weren't as close as the start, so i was like its not working out, and so i broke up with him. time has passed since the break up, and i find myself thinking about him, the good times, and when i see him, its like my heart rapidly increases, idk why i shouldve been over him a long time ago, but no.... is it normal to feel this way?