Husband still tells his high school sweetheart he loves her poo

So my husband and I have been together for almost 7 years married for a few months. He's 33 and I'm a week away from 31, anyway.... we share a laptop in our living room and he has his own computer for gaming and internet in our bedroom. I got on the laptop today and his Facebook was open to a conversation he was having with his high school sweetheart...Some back story: They broke up in 2005 or 2006 and from what he's told me she shattered his heart when she broke things off. She then slept with his best friend at a party they were all at a few months later. So salt on the wounds is where she left it until spring of this year. She messaged him about checking in a mutual friend's mom who lives alone in our town, he agreed and then they got to chatting. She apologized for treating him so badly and they talked about life, her marriage, 2 kids with one on the way, and caught up. He told me about it but not in detail No big deal. Today see that the were talking again and he told her " I miss you, love you and if you need anything I'm here for you love! " They had only been talking about the holidays and how family was doing. Nothing sad or bad was going on that would warrant that kind of response. I feel like I could be reading into it to much or he really still has feeling for her. He once referred to her as the one who got away so it just doesn't sit well with me. I don't care that they talk, but it just strikes me as he's being too friendly. Desperate almost... Am I crazy?

Update: So I decided to go back and snoop the messages to see if any other conversations were out of line. It seemed like on her end it was more about forgiveness and friendship. On his side there's some red flags, these messages were from before we got married, but still we were engaged. She told him about depression she had and a time she had truly contemplated suicide to which he replied he was glad she didn't go through with it (which I am too as I've been there and no one should have to feel like no one cares) but here's where his response gets hurtful... she said she wanted to be friends and repair the friendship that she broke. He replied that he also wants the friendship and that he's happy that she thinks about him from time to time! I'm not friends with my high school sweetheart nor do I talk to him anymore ( I am friends worn his mom and siblings just not him) my high school sweetheart just married his wife in November and I don't think it's an appropriate relationship if I were to talk to him. So now comes the part where I figure out what I'm going to say and talk about with my hubby if this is going to work or if we go our separate ways so early in marriage. Wish me luck.