Well, what you have here is a man who does not, IMO, respect you. He may be fond of you, attracted to you, "love" you (whatever that means to him, but he doesn't respect you because he won't do what you ask which is not to have these inappropriate conversations and texts with these women, especially A. He can't seem to stop talking to A in some way so....I have to ask him...what is the attraction to A....why can't you stop talking or texting or liking her bullshit on IG, etc. Why do you do this? Why do you honor her with your company instead of me with your fidelity. Why don't you respect the trust and the 2nd chances I give you? Do you have NO SELF CONTROL? What is wrong with you, man, what are you getting out of this thing with A. And it's true of the others too.
I am NOT a fan of opposite sex relationships, I think they are inherently a bad idea....for the obvious reason you see. Unless there's a big age difference or one of them is ugly (even that's not always a stop) the normal emotional and intellectual attraction between friends often has a physical element too....in oppo sex relationships. Maybe nothing happens, but I feel that the door.....is open. It's open to some extent. And the attention that is paid to an oppo sex "friend" is attention that is missing from the spouse. Especially if you think something more if going on....which realistically is often the case.
So I feel he doesn't respect you, he consistently violates the boundaries you valiantly and kindly put up, trying to keep things together. He's gonna keep doing this especially if he thinks you'll keep forgiving him, which you have.
I always ask people what do you WANT IN LIFE? What do you personally want to achieve, how do you want to be treated, what are your values? What are your lines in the sand? What do you want out of a relationship? I think you need to define these things about yourself because that gives you a solid basis to act from....knowing yourself means knowing what you will and will not deal with. It makes you strong, even if sometimes it makes you sad. Learn to be strong.
If I were you, I would be talking to a lawyer and looking at divorce. I don't know the laws of course, in Spain, but you need to check this out and find out what is the best you can work out for you and your kids. And when you have that to your satisfaction....start the process. If he realizes that you ARE SERIOUS ABOUT THIS...maybe it will help to catapult him into starting to change himself. Choosing MALE FRIENDSHIPS over women that seem like a challenge to you and your position. For things to change, somebody has to start the change. I think he's just gonna keep doing this until YOU start the change. So, as hard as I know it is, that's what I would do.
You can talk to a therapist for your own needs and goals but I don't know helpful it will be to talk as a couple because he's just gonna bullsht that person and you too. The bullshit has to stop.
Stay with us, there's a lot of other advice and support here, I'm only one person, others will have other perspectives and you'll get a lot of help. It's an excellent site and the people are very caring. Do not be afraid, God is always with you even in the dark. No matter what happens you will come out of this a stronger and wiser person. Good luck!