I'll attempt to keep this short!
DH has made a female friend through one of his hobbies. At first I didn't think much of it but there have been a few things that have made me worry.
First issue, I had plans to go away one weekend with friends. Earlier that week I was lying in bed and DH's phone started buzzing. I glanced at his phone (he has text previews on his lock screen) and saw messages from this woman about meeting up with him to do their hobby at the weekend. He hadn't mentioned this to me so I asked him what he was planning to do while I was away and again, he didn't mention it. I said I knew he was lying as I'd seen the message preview and he said he didn't mention making plans with her because he'd changed his mind and was going to do something with another (male) friend instead. That turned out to be true so I gave him the benefit of the doubt.
Two weeks later, a giant parcel turns up for DH. He opened it and it was a gift from this woman. There was no apparent reason for the gift e.g. not his birthday or anything. I said it was weird and made me uncomfortable and he got really defensive and said she's just a friend and I needed to calm down.
Since the gift, he hasn't mentioned her at all. Then last night, DH's phone beeped while he was out of the room. I looked at the screen and could see a text preview from this woman. When he came back, I said "your phone's been buzzing" and he replied "oh, it's just a work email". My heart sank when I knew he lied to me so I waited until he went to sleep and then snooped through his phone. I read through their entire text history - there are hundreds of messages going back over the past few months. There was nothing in them that suggests they are anything more than friends but they are texting almost daily and DH is hiding this. If anything, the conversation seems weird and a bit one sided - most chats are initiated by her and she is sharing a lot of personal/emotional information with him (e.g. looong texts about her mental health). DH doesn't seem to be sharing much with her and is quite abrupt in his responses.
So as the title suggests, should I be worried?