Is it wrong to still be friends with an ex that I won't act on but still have feelings for?

My ex and I communicate on a regular basis usually on the internet but sometimes we will call each other. We will never be in a situation to meet up or anything (I wouldn't trust myself if I did).

I love my husband but there's a small part missing in him that I find with my ex and it's satisfied just by talking to him.

Am I being wrong to talk to him behind my husband's back? Am I leading my ex on (he isn't seeing anyone)? Should I stop it all together?

I'm so confused!