Are you sure that she started texting him first? Have you got the whole story here?
I can only agree with other posters. You have taken the blame for him not being happy and in some perverse way you are trying to make up for the fact that he betrayed you. Instead of apportioning blame onto him you are blaming yourself and the woman who was your friend.
Let me ask you; who betrayed you the most? Your husband or your friend? Who made vows to you in front of an audience? Who made a commitment to you?
Even if she had started texting him, is that all it takes to lead him astray? Could he not have ignored her? You see, she must have known he fancied her for her to have approached him in the first place.
Even a "blokes bloke" knows it is wrong to cheat on your wife, the mother of your children. Being one of the lads is no excuse. He does have half a brain does he not? He is responsible for his actions?
Even if Angelina Jolie were to drape herself over my husband and whisper sweet nothings in his ear I would EXPECT him to walk away. Because he made vows to ME and he has a choice. Just as I would turn away from my fantasy shag because in reality I also chose my husband above any other.
Your husband is telling you that he no longer loves you. Well, no, he isn't telling you because he's a coward but he's giving you some pretty big hints that you just aren't taking. The more he hints the more desperate you become.
He should be doing everything in his power to make it up to you. He should be showering you with affection, apologising over and over, suggesting counselling, whisking you off on romantic breaks - in short he betrayed you and he is the one who needs to not only take full responsibility for that but also to save his marriage. He's not doing that which sadly means that he doesn't want to save it.
You are the only one who thinks there is something to save but really, you are flogging a dead horse. The way he allows you to blame yourself for his actions says it all. You are doing all the running and for what?
You will never get back what you thought you once had because it never existed. Clearly he was unhappy before and that cannot be resolved because he is unhappy with you as his wife. I'm sorry but that's the way it seems. Only he's too cowardly to tell you that.
I bet if you suggested you both break up he'll be only too keen to get the ball rolling.
Confide in your family, lean on the shoulder of a friend and accept that this is probably the end of the road for you both. You did your best which is more than he did. You are not to blame for his actions or his choices. You cannot and should not change who you are for anyone. They either accept you or they fuck off.
I think you might need some counselling to come to terms with this and to raise your self esteem as you sound like someone who is very low on confidence.