His ex popped up on his insta

Sooo guy I’ve been talking and seeing posted a hiking pic today on his insta. I did snooping weeks ago and noted he and his ex still follow each other and she has couple pics of them still up on her page but not his. Anyways she commented under his post and he liked it. It was a cutesy pet name she had in one of their couple pics. Should I be concerned?? No I’m not insecure but if your ex is commenting and liking your post congratulating you, calling you a pet name with a heart eye emoji at the end? Ummmm. I remember him telling me about her early on when we started talking and I asked what happened and he “claims” they were together for 2 years, broke up. Rekindled a few months later to try again and the. she got together with an old fling while he was away on a trip and ended it right then and there. I feel like I’m the 3rd wheel here suddenly? I’m afraid to ask because we’re not exclusive but at the same time don’t want to waste my time on a guy if there’s something going on between them??