“I had to have this talk with you
I hope you understand
I don't have any plans with you
I'm someone else's man”
-Ewert and the Two Dragons, Jolene
Dating isn’t marriage, and it’s wrong to treat it with the same sacred exclusivity that we reserve for marriage. By itself going out with more than one person at the same time isn’t a “sin”. There may be a number of people you think could make good spouses and so you want to get to know them all so that you can make an informed decision! This may not be the wisest way of dating as you could get a reputation of being a flirt or a player, but it's not sin.
What IS sin is to be deceptive about the fact you are seeing others. You should not go out with a person and leave them thinking they have an “exclusive” relationship with you if you are also seeing someone else. If you are just getting to know someone who is one possibility among a many, then be honest and upfront about it lest you cause emotional damage.