Mandatory bathing for a new Muslim.

Q; Brother I am revert. Someone told me that when I became Muslim, it was mandatory to perform Ghusl as a sign of purification from shirk. I didnt know anything about such ruling. I didnt take Ghusl after taking Shahadah, but always purified myself by taking Ghusl after completing menstruation, post natal bleeding and janabah. was it necessary to perform Ghusl upon taking Shahadah? If it was so then am I still impure? what is the ruling on this.

A; Sorry for the late reply as for your answer to your question:

All-Praise is due to Allah,

The opinion that we hold from among our Scholars is that it is mandatory (Fard) for the one whom enters Islam to bath. 

It states in the Ansaf (12/241): It is compulsory to bathe upon those whom enter Islam unconditionally. 

Ibn Quodamah said:   ...and if the disbeliever becomes Muslim it is mandatory for him to bathe, whether he was a disbeliever or an apostate, whether he washed just before he became a Muslim or didn't wash at all, even if there was a mandatory reason for bathing that occurred in time of disbelief or no reason. End of quote. 

[Al-Mugni: 1/132].

The evidence that relates to this is the Hadith that is related by Qays bin  abi Hazim came to the Prophet ﷺ said I would like to become Muslim, so he ordered me to bathe in water and Sidr (Ziziphus root). 

Related by abo Dawoud : (355), and Al-Albaani grades it as authentic in Irwa Al-Galil: (1/164).

As in your case you don't have to bathe, because the very fact that you have been a Muslim for a long period of time which makes your regular ritual bathing for worship suffice. 

And Allah knows best...