i need advice please

my 3 year old son on the verge being kicked out of preschool cuz od his behavior. hitting kids. spitting at them showing his private areas.they teachers have tried a much of different apprches with him nothing is working an gerting worse. got sent home today for spitting in a little girls face. i have tried talking time out taking things away spanking him on the butt. i dont want any bashing moms please nothing but support an advice. only thing different is im pregnant i include him in thingswith the baby i have taken him to appointments i also asked him if hes upset about having a sister he said no he happy. he says he likes his school an people are nice hes being a bully an hrs i would say a mean kid. even at home having a hard time. listen any advice. should i even send him to school tomorrow. i feel embarrassed he has an appointment over the summer July t into aug to be seen by a doctor to be evulated but im in a lost what to do. he terrible im in over my head on top that my husbands in deep depression