At the age of 3.5 years, I think your child need not have a diagnosis or medicines for this. However, you can consult a psychiatrist for detailed assessment and to rule out the possibility of neurodevelopmental disorders. Behavioural therapy only is suggested at this age in most cases. To start medicines, it is recommended to wait till 6-7 years of age.
Next Steps
Consult a psychiatrist for assessment and to get guidance regarding behavioural therapy. If you wish, you can consult me online.