It is common – I suffered too but it did eventually recover.
Try not to worry about this for a start because this can make things worse.
It is really just down to hormonal upheaval and takes longer to settle in some women. You will not lose it all. Do not forget what an upheaval to the body giving birth is and you have done it 3 times so 5 months is really not a long time.
Try to be gentle with your hair and avoid over brushing or fastening it up too much, and do not use too many products.
Treat it gently as you would any other part of your body that is healing.
Also speak to your hairdresser – she should be able to advise and reassure you.
Good luck

It will last forever.