I'm breaking up with you!

I have been with my partner for 11 years, we have 2 children together, 4 and 5, and until this morning as far as I knew we were a happy family. After missing the bus to go Christmas shopping earlier today, myself and my 2 daughters returned home, my partner wasn't doing anything when we walked back in but she looked visibly guilty on her face. It's hard to describe, but it's like she was caught doing something she knew she shouldn't be doing. I noticed her phone had been pushed to the floor beside her. She then said she was going to phone somebody and went in the other room and shut the door. A moment later I went in and noticed that she wasn't on the phone but was on messenger. I didn't say anything. I was using her phone a short while later and curiosity got the better of me. I looked through her messages to discover messages to and from a male work colleague, which were playfully flirty in tone. I again didn't say anything. Later on in the day, I made a point of using her phone again, but when I looked at messenger, the messages had been deleted. Now I'm not a paranoid person, I trust(ed) my partner, but we are usually very open with our social media accounts regularly going on each others accounts as we have(had) nothing to hide. But this didn't add up to me, so I asked to have a chat with her, away from the children, so I could confront her on this. I politely asked her who this person was, to which she tried to laugh it off as something innocent, but when I pried a little more and asked her why she had been talking to this person in such a way, she blurted out "because I'm breaking up with you". My world shattered. She insists that infact talking to this other guy has nothing to do with breaking up with me and gave me 3 reasons why she is, I'm grumpy, I'm controlling, and I'm stubborn. I am grumpy and stubborn but for her to say I'm controlling sounds like someone else's words. She has also admitted to me that she talks to him about our relationship and how much she dislikes me at times. The "controlling" comment she made sounds to me like something he may have said about me. She has also told me that she hasn't even spoke to her best friend about maybe breaking up with me, just this guy, it makes me feel like he's manipulating her for his own agenda. However, in the face of losing her, I have not dwelled on the fact I caught her inappropriately messaging someone else, as I will do anything it takes to atleast try to work through this. I've since tried talking to her, but she is not very respondent. She says she doesn't know if she wants to work through it as she hasn't been happy in a long time and she just needs space, which I've agreed to, however is a little difficult considering we have children together. But this is the very first time she has ever said anything of the sort to me, I'm not a mind reader. I don't think it's fair for her to just throw 11 years away without even trying to work at it together. She told me she was going to wait until after christmas to break up with me, but then I found the messages so did it now, which in itself is contradictory to the claim by her that they are unrelated. With our work schedule at the moment we barely have 10 mins quality time a day together through the week, as she works days and I work nights, so it has been a particularly hard couple of months for us. I think she has been feeling lonely/unloved, and has turned to a male friend who has been flirtatious towards her to make herself feel better about herself. I think that maybe she has said she's breaking up with me as almost like a defense for her being caught out. I'm a total wreck and have no idea what to say or do. I want to fight for this relationship with everything I have but don't know how. I've owned my flaws that she pointed out, and have readily accepted making drastic changes to myself for the better. But she still wont say whether she's willing to at very least try to work on it together. I'm petrified of the outcome of her having time to think about it. I love her soo much, she's been my world for a very long time. Any advice welcome, please.

If you're just catching this chances are it's been going on for a while. And to be honest your schedules made it very easy for her to get away with it if it had been going on for a while. You have to let her learn for herself that the person she's paying attention to is no looking to build a family just wants to stroke his own ego knowing he can be with another man's wife. And If she's willing to let go of 11 years and two kids just like that you owe it to yourself to not hold her back it seems like things are in too deep and she just has to learn the hard way.