I split with my girlfriend last August and quickly met my current girlfriend very soon after (3 weeks) due to me deciding to move on cause I knew my ex was seeing someone new and to be honest I couldn't really cope. My ex had left all her stuff at mine so we remained in contact (some of which we argued) till she got settled and picked it all up.
At this point I cut all contact however my ex does still text me normally around 2 week intervals or writes on my fb account, most of the time I ignore her and have stopped going on fb but at xmas I thought it polite to answer the merry xmas text she had sent and we had a conversation. I made my new girlfriend aware of this much to her displeasure but thought honesty is the best way.
However since the conversation I realize I do still care for my ex and I'm fairly sure she does me, the latest conversation we were having she asked me if I'm still with my girlfriend and when I replied yes, how about you, you seeing anyone? She has not replied. Most of the other conversations we have I do get the feeling there might be something there, my only problem is that I want to know what's in her head, is she interested or not? I know that's she had other boyfriends since me. Is she just after mr reliable again and the easy option?
We were together for a year and some of that we were living together we split because she needed to be on her own, she suffers with depression

Now that you are in a relationship, it's not fair to your current girlfriend to be trying to respark things with your ex.

Figure out whether you want to continue staying in this relationship before you worry about possibilities another girl, even if that means going back to an ex.

Be fair to your current relationship and don't drag things out if you don't believe that it should continue.