Your first love will always be that. You don't get to take it back or switch it for another person. They'll always be your first. I was fortunate that my first also turned out to be my wife. We dated back in 2000, broke up, she moved away, started seeing other people, we kept in touch. I visited her in various cities, she visited me - as friends without benefits.
And then by some curious twist of fate I ended up going out to Switzerland to visit a friend with benefits and do some snowboarding. As it turns out that my wife had moved to the same city in Switzerland so at one point we all ended up out partying and well, one thing led to another. Needless to say both of the girls I was doing at the time weren't too happy about me and her being 'back together', as it were so I left some hard feelings in Switzerland.
But in the end, fuck 'em. I knew what I wanted out of life.