I feel vindictive

My husband has treated me poorly ever since I gave birth and during the cause of this I found out he has been having an affair.. I am 4 months pp and honestly I have tried as regard intimacy .. but knowing he cheated or probably still cheating has me really messed up . I want to pay him back , I want to make him feel the pain in my heart but I am not that woman . When i checked his phone and saw all the mess he has been and how he presented me even to his friends I felt so torn that in the cause of the argument I slapped him twice . Everyone says I shouldn’t have and honestly I regret hitting him because in my life I have never raised my hands on anyone.. to see a man I love and respect so much treat me like shit, manipulate and gaslight tears my soul apart . We are just 1year in the marriage and I feel tied because I have a 4month old , no job since I got pregnant (had a difficult pregnancy) so I can’t even walk away . My heart hurts mamas 😔😭 To get a job i can’t even afford a childminder coupled with PPD .. I honestly need help