Partner (23M) is clearing conversations with his colleague

For context my boyfriend (23M) and I (22F) have been together for 9 years (A tween relationship that never ended).

He works in construction and has been for the past 2 years. Mid last year he moved to a new site where he met a couple around our age and befriended them. Since then my partner and the girl have added each other on snapchat.

In January of this year I found her in his recents with a bunch of snaps between each other, I also noticed they had a streak. I asked my partner why he didn’t tell me they were snapchatting and asked what they were talking about, he said he forgot to tell me and that it was just blank snaps between each other and mentioned it was only a one off conversation. I called him out on his bullshit because they had a streak meaning they had been talking everyday for the past week and he just sat there with no excuse but apologised. I let it go.

A week later I saw the streak was still going with them meaning he hadn’t cut it off or told me anything about it, I brought it up again and he apologised saying it was “work stuff”. I let it go again.

About a month later I caught myself thinking about the situation and looked at his snapchat again. She was no where to be found in his snapchat which was odd since I knew they’d talked the month prior. I looked her name up in his snapchat and saw there had been snaps between them that week and not only had not told me he also cleared their conversation. When I brought this up to him he said what are you talking about and denied it, when I showed him he said “I only cleared it because I knew you’d get upset” …. what the fuck. I gave him a hard time about it and let it go again.

Fast forward to last week I found he’d been talking to her again and he didn’t tell me. I didn’t bring it up but this week I went to bring it up and show him but noticed he’d cleared the conversation with her again. I got upset to say the least and questioned how he could keep repeating the same thing when I’ve only asked for him to communicate with me about it.

Do you think I’m overreacting? I need advice on what to do.

TL;DR: My boyfriend hasn’t communicated with me about snapchats with his female colleague multiple times and cleared conversations. I need advice on what to do going forward.