If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at (Phone number can only be seen by the question and answer creators). Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe dizziness, irregular heartbeat, mental/mood changes (such as agitation).

I doubt it would do you any harm. People's natural dopamine levels vary all the time, depending on activity and diet. You might have just felt really good for a while.