We must do shalawat when rasulullah is mentioned or referred by other people, but how if it is us/myself who mention or refer it, do i have to do shalawat every time i mention/refer him?.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Exalting the mention of the Prophet is a good deed, and it is one of the greatest acts of worship by which one gets closer to Allah.

It is sufficient for you that Allah invokes blessings upon you and forgives you ten times when you exalt the mention of the Prophet once.

Exalting the mention of the Prophet is required whether you heard his name from someone else or it is you who mentioned his name, because the Prophet, said: "The miser is the one in whose presence I am mentioned but he does not exalt my mention." [At-Tirmithi]

The Prophet also said: "May the man before whom I am mentioned – and he does not Exalt my mention – be humiliated." [At-Tirmithi]

However, it is not obligatory to Exalt his mention every time you mention his honorable name; this is only recommended. Therefore, you are not sinful if you do not exalt his mention, when mentioning his honorable name many times, yet it is better for you and greater in reward.

For more benefit on the virtues of invoking blessings upon the Prophet, please refer to Fatwa 86784. 

Allah Knows best.