Me.and my ex ended the same way, there was an age gap and I didnt like going out as much as her, but she wud go out alot and dance and flirt with people and get their numbers 'to be friendly' but would then text them alot and also confessed wen we split in Jan that she'd been talking to a girl online and had arranged to meet up but didnt at the last minute, and I knew nothing about it!! But of course all this was my fault cus I was too focused on ttc. And to top it all off, we split cus she didnt wana settle down, yet started a relationship and moved in with one of our friends who I used to go mad at her texting 24/7 (who was in a 4 year relationship at the time wen they text/skyped all the time!)
I think u both need to have a proper talk, maybe he just likes the attention, but it cud be more than that and its better to know now rather than later!