Negative thoughts are as common or more frequent than positive thoughts in every being. It's not possible to think positive all the time. What matters is the frequency and the intensity of these negative thoughts. Weather these are thoughts about self, others or future. Thanking help from a psychologist will be helpful and he will make a action plan for you and some thought restructuring is needed.
Next Steps
See an expert in thought restructuring or CBT
Health Tips
If the intensity and severity of thoughts is high & if the psychologist says only then see a psychiatrist.