help, irregular periods and breastfeeding

Hello, my baby is almost 15 months old and we still breastfeed.

My period has been coming pretty regularly since my daughter turned about 5/6 months old but they were always late.

Last month i had a normal period but this month I haven't started at all? I am worried about pregnancy because I don't want another baby this soon.

My husband and I do use protection when we "get" to have sex. Is it normal to be this late during breastfeeding?

My daughter still breastfeeds on demand but she of course eats solid foods too....she also nurses through out the night since she sleeps with me she just nurses most of the night.