This should be time you have alone perhaps when the children are in bed and to make sure it is distraction free (with the computer and TV turned off).
How much of a problem it is, depends on the degree and type of access and what it means in the context of the marriage.
Up until this, I thought things were okay in our marriage, though of course we haven’t had much couple time with the demands of four children but this discovery has come as a bolt out of the blue.
It wouldn’t have been as bad if he was just accessing porn, as I know men do this, but the fact that he was talking to other people has really disgusted me.
Of course your husband should not blame you and he must take responsibility for how he has hurt you with his online behaviour, but the two of you must take responsibility for improving the marriage.
Though it may be painful, the fact that you have started talking about issues is a good sign.