@Mango1234 There are a few factors that will affect how fixable this is:
It matters how he found out - did you volunteer a confession, or did someone tell him, or did he discover it himself ?
It matters when he found out - was the affair ongoing when he found out, had it just finished, or was it long finished?
It matters who the affair partner was - did he know the man, had you introduced him as a 'friend', did he know you were attending events with this man thinking it was platonic?
It matters how your sex life was previously - did you have an active sex life with your husband, did you do what he wanted in bed, did you climax with your husband frequently, will he feel emasculated imagining that your affair partner was better in bed then him?
It matters what the reason for the affair was (which you have not told us - loneliness is too general a catch all) - were you sexless, fallen out of love with him, had he let his appearance and physical appearance go, had you been living as cohabitating parents?
It matters what you have told him the reason for the affair was - did you tell him that his job requiring travel forced you to do this (i.e. you blamed him), did you just say that you were sorry and offered no explanation, did you offer a full and open explanation taking full responsibility?