1 year old help

Ok I wanna start off by saying yes I understand one year Olds are still little they dont understand I dont know if its all these hormones from this pregnancy but its like I'm losing it i am so overwhelmed and my second child isnt even born yet my doctor wants me to take it easy because I have 2 tears around my placenta but it seams as tho my son thinks now would be the best time to stop listening and do literally everything his not supposed to which I get its the age hes at but he would somewhat understand before if I smacked his hand or but and told him no that he wasnt supposed to do that but when I do that now he just keeps going back and doing the same thing over and over and will mskr sure I know hes doing it i don't want to yell at him so much it breaks my heart I need advise