I have lost both my mum and dad and in each case the grief came differently. There is no 'right' way to grieve. Generally it follows a pattern or cycle but people react in different ways.
It is common that it can hit hard after 4 - 6 months so be prepared for this and have friends and family to support you.
I was an only child and it can be doubly hard for us. There's no-one else to support us and we are often very close to our parents. So for those who are suffering loss - take heart - you are not alone. remember the good things about your loved one. They are always with you - in your heart and mind. What would they want for you? Listen to them 'talking' to you and feel their love support you.