I am a born Healer. Shall I learn Reiki still?

YES!

The answer is yes.
We all are born healers. Some of us remember it and some of us don't. It is easy for those not remembering to learn and accepts someone as their teachers. But for those who remember their essential nature as healers cannot accept teachers easily.
They too have problems and fears like others. They too face difficulties and tight spots during the healings. Some of them may even feel need to do protection. There are other issues that arise with healings. So those who are not under guidance can easily feel lost.

So even if you are born healer you should learn some techniques of healing to equip you with better tools and handle difficult situations easily. Reiki is one of the most simple, easy and quick way to recollect and learn. It is also a good stepping stone. It is good to surrender and be open to knowledge.