Under which head my Income is Taxable?

I'm a builder. I always used to buy a land and build a house or shops etc. on it and sale it. it is my ordinary course of business. Generally after completion of construction within 2-3 Month I sold house or as a case may be.
4 year ago I purchased a land and built 2 houses but i unfortunately I couldn't sold it and as a result I'm still owner of it.
Now I'm got customer for this and I sold it in March 2018 but registration will be after March i.e. In April 2018

Please guide me that should I pay tax under The Head Capital Gain or Income from business and profession ??
please note that it is my normal course of business
is any provision that if builder is not sold building within 2 year that it is treated as capital Gain??