NC for this as there's some personal details.
In late 2016 I was on Match and started dating someone (I'll call him MG for Match Guy). Went on a couple of "proper" dates and began seeing each other every couple of weeks (both had DC and worked full time so hard to get the time). We were sleeping together, I wasn't seeing anyone else but that was more down to free time than anything. We weren't officially in a relationship although for a while I thought it was heading that way. However it was never really relationshippy - we would chat frequently but there was always a bit of distance between us. That was OK, I was coming out of a long term relationship and not looking for anything serious.
The week before Christmas 2016 I went to his house one afternoon, we had sex, I went off to do my Christmas things with family. We texted a few times the next day then he ghosted me! I was annoyed at the rudeness but not heartbroken, and just left it at that.
Three months later he got back in touch. I told him off for ghosting me. By this time I had no illusions about him being relationship material but I thought he'd be OK to keep around as a FWB. We began a lot of sexting (which had always been part of it but now it ramped up). We met once for sex which was OK, but he really just wanted to sext, even though I was offering FWB and I thought he'd prefer the real thing to chat! In the end I got fed up with this, it wasn't doing it for me and I faded him out.
As it happened a couple of months later I met my DP and was smitten from the off, the difference was striking and we began a relationship.
MG would text me infrequently but I never engaged. I told him I was seeing someone and expected that to be the end of it. In fact he would text me every so often, usually late at night, even though I never replied.
The other night he did it again, sending me a bloody heart-eye emoji! Bear in mind this is on the back of about 7 messages that I'd just left on read! So as I was bored I looked on his twitter and saw a post that referred to a "2 year anniversary" in December last year! In other words he's been seeing someone seriously this whole time! Ugh. I would never have met up with him if I'd known that, but he's still fishing around me.
My first reaction was just "ugh, GROSS", but it's two days later and it's really playing on my mind. Why??? I was never hung up on him, wouldn't touch him with a barge pole now and am with my amazing DP who I love truly. I never loved MG and often felt like he wasn't even that likeable. Why am I so annoyed about this discovery?
Sorry for the long post, I just felt like I needed to vent but didn't want to share the gory details with anyone IRL.