Received a call from an "ex" and I'm now not feeling the same towards my current boyfriend...advise please..?

He's your "ex" for a reason. Don't feel different towards your current boyfriend just because he called you. At the end of the day you have to make the decision that's best for you but remember it's a balance between your old love and your new love. You can easily tip in the wrong direction but you have to be willing to take the fall and all the consequences for whatever your choice is.