period after birth

hi!
i am writing in English because i am in the u.s. and i don't have Hebrew here, sorry.
i am just a little worried: i gave birth 6.18 month a go. i was breast-feeding fully until the end of the third month and another month i was breast feeding 2 times a day. i had a very short and little period at around the beginning of the fifth month and until now i didn't have anything any more.
is that OK and normal?
thanks allot...
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