Does he still have feelings for her?

So about 6 months ago I discovered that my boyfriend had been hiding messages from an ex fling he had over a year ago. Her messages were muted so I didn't know when she was messaging him. He also called her "Panda" as that was her nickname. I was upset about this for months and even more so I questioned him about her and he lied to me. I eventually told him I had seen these messages knowing it was wrong of me to go snooping and I always had my concerns. Constantly playing in the back of my mind if he still has feelings for her. He told me way before we got together that she meant a lot to him and he wanted a family with her. When I told him he didn't have a lot to say. Just said it was her messaging him and he didn't care for her. I thought this was the end of the messages until I picked up on him being a little odd with his phone one night and seeing he was ignoring messages. I asked who it was and he said it was me just sending him funny videos as we used to find them entertaining to send to each other. I believed it as I didn't get the notification he had seen it. But why didn't he open it if that was the case? I went through his phone again a few days after to see she was back. There was deleted messages as the conversation starter didn't make sense. It was like she was replying to him and was telling him how she is and she has drama with her kids. He replied back to her a massive paragraph saying how he has drama at work and he wants to leave and get a new job. Then went on to ask her what the drama is with her kids. This was all I saw as she hadn't replied. I don't know how to feel other than frustrated he can't leave her alone.