Would you consider this crossing the line

[RainbowBrite1]

My DH of 15 year we are early 40s with two little boys. I'm not working at the moment and take care of the boys and do all the house work.
My DH has worked at a company for about 2 years now and until recently I never once heard him mention this colleague. He very casually dropped her name into a conversation one night a couple of weeks ago.
He told me last week I was invited out on a
works night out but I could see on his face he didn't want me to go I said I didn't have child care. He went I felt something off so the night after I checked his phone. Probably 100 messages over a few months probably 10 or so which I'd consider inappropriate for a married man. Kisses and one with hearts on the end. In one he said she means the world to him and wants her in his life forever. I've confronted him. He thinks I'm making something out of nothing. I also got her some gifts from lush for Christmas I was in when the parcel arrived I thought it was me but it wasn't because I got nothing from lush at Christmas. Help me am I overreacting. Thank you

Yes. Completely crossed the line.
He's broken your marriage vows by emotionally cheating.

For me whether it was possible to save the marriage would depend on his reaction. The fact that he's dismissing your pain doesn't bode well.

Yes, sorry Op but that's perilously close to an affair. He didn't want you to meet her at the works event, that's not a good sign, he got her a Christmas present and puts kisses on his messages to her - it may not be an affair yet but he'd like it to be

If it's not an affair already then he is certainly heading that way. He'd be livid i you were behaving like this.

There's nothing for it but to confront him. If he plans to continue like this then the marriage is over. He'll try everything (look up DARVO - Wikipedia) but if he's in the throes of it now there'll be little that you can do. Sometimes the threat of a divorce and not seeing his child every day etc will do the trick but often it doesn't, I'm afraid.

Thank you. I was thinking the same but but wanted a 2nd opinion

Absolutely. I wouldn’t accept this at all. If he hasn’t cheated physically he’s doing it emotionally.

Sorry OP that sounds like he's cheating or planning to. You are not overreacting.
The fact that he didn't want you to be there at the work do (where I'm guessing she would also be) speaks volumes.