I've namechanged for this, and changed all names of people involved.
Last week, DP and I were out for dinner with his sister and her partner. We were all just chatting away and SIL said, "blast from the past; guess who messaged me on Facebook the other week - Jen Johnson!" I already know that Jen was DP's first proper girlfriend from almost 20 years ago, and that she was very close to SIL as well as all their family. DP and SIL chatted about Jen and her brothers for a bit, then topic moved on.
A few days afterwards, DP said to me entirely unprompted, "you know how we were talking about Jen at dinner - I've already decided that if she contacts me on Facebook or suggests to [SIL] that we meet up, I'm not going to respond to her because my life is with you now, and I noticed that you went very quiet when we were talking about her." I replied that I only went quiet because I couldn't really join in with a conversation about somebody I'd never met, that it didn't upset me in the slightest that she'd been a topic of conversation, that I don't feel 'threatened' by the idea of him having ex-girlfriends, and that if he wanted to get in touch with her for old time's sake then not to let me stop him as it wouldn't bother me. All true. He said that even so, he didn't feel the need to contact her.
Yesterday, I was using his Facebook account (I don't have my own account but use his occasionally to keep in touch with our mutual friends, which he knows about) and noticed that he made a friend request to and exchanged messages with Jen a couple of days after the dinner with SIL but before the day where he said to me that he wouldn't want to have contact with her. I also noticed that one of Jen's very recent status updates is "Oh, that weird weird feeling when THE lost love of your life pops up in your life and it's like you're both young again, all mistakes unmade and you suddenly feel like you have a chance to say the stuff that should have been said twenty years ago. Seize the day, people."
She's married, according to her profile and what SIL had already said.
For context, this is the second time that DP has said something to me, unprompted, about one of his ex-girlfriends, which turned out to be totally untrue: about a year ago he said to me out of the blue, of his most recent ex-girlfriend: "You know, I never had any real feelings for Sophie and I never told her that I loved her or anything." I hadn't asked anything about her or given any indication of feeling insecure or comparing our relationship to his previous ones. I later discovered through friends of his that he very much had told Sophie he loved her and that for somebody with no real feelings he'd certainly done a very good job of showing otherwise by discussing with one of his friends about asking her to marry him at one stage. Have never mentioned that I know this to him.
I don't know what to think. I generally believe Facebook to be the work of the devil with all the hearsay and gossip and seven degrees-ness of it, and don't want to use things I've read on it as the basis for confronting him. But if I don't, I'm always going to wonder why he'd tell me one thing whilst having already done the opposite, aren't I? What's he playing at? :(