Are repetitive thoughts about a past relationship normal?

[Destiny]

I got out of my first relationship over eight months ago, and I still think about it every day, sometimes every hour. I don't necessarily think about HIM but about the relationship in general, and I'm constantly having flashbacks. I should also note that he was my first relationship, not to mention my first kiss, first date, and I also lost my virginity to him. The relationship got very serious very fast and he ended up breaking up with me out of nowhere and pursued another girl. I know not thinking or talking about me anymore, so it greatly frustrates me that I cannot do the same. Sometimes I feel like my constant thoughts about the relationship occur so often that it feels almost obsessive. I have not tried to contact him in over seven months, and I am actually quite content with my life right now. I'm a full time student with a part time job, and I haven't dated anyone since the break-up but I have friends and a social life. I mean I'm not exactly a party person but I'm not lonely in the social sense. I'm functioning well, I pull good grades. But every single day since the relationship ended has been ridden with thoughts about what happened, how much it hurt, and I just don't know what to do anymore. I don't like having these constant thoughts, and I wish there was just some way I could make them stop. So, what should I do? This surely can't be normal, so should I maybe seek out therapy?