Avoid hair oil usage, it never helps for the hair growth.
The hair cycle normally consists of growing, resting and falling hairs and there is a delicate balance between these stages of hair cycle. Normally hair should regrow but if it is not happening, you should consider seeing a dermatologist.
Next Steps
Meet a Dermatologist.
Health Tips
Further information is in the following weblink https://www.aad.org/public/diseases/hair-and-scalp-problems/hair-loss