Not sure what I should do about my ex girlfriend

Maybe there is still a spark there,theres nothing wrong talking to your ex so don't listen to others,..unless of coarse the breakup was brutal.

You need to figure out if those feelings could develop to something much greater or just simmer down.

It's not uncommon to think about ex's, but do you really miss your ex or are you curious as to what could be /could have been?
Maybe you two just had a physical attraction, or maybe something deep could come out of this..

Think about why you two broke up to begin with and see if it could have something to do with that..maybe she misses you because she has unfinished business.

First of all what are you still doing talking to your ex in the first place? Think about this: Could it be possible that now that her relationship is over she's lonely and wants you back? And if you did get back with her how quick would it be for her to look for "something better" and leave you for someone else? She broke up with you once. Its normal to think back on a person but not all the time. Weather you end up dating this girl or being single you may need to leave your current girlfriend. Its called cheating of the heart. How would you feel if the situation were reversed and she wanted to be with someone else but kept stringing you along. I mean you did say that you DEFINITELY felt something for your ex. Thats not cool. You and your current girlfriend need to sit down and have a serious conversation. And if you are just bored than that's your fault for not communicating to your partner about what you need in your relationship. Spice things up. Do something spontaneous and different. Break out of your rut. I dunno. Only you know how you feel.

There is a saying that goes: Dont leave the one you love for the one you like, because the one you like will leave you for the one they love.