By the 5th month, you are into the territory that you are more in the supply/demand of breastfeeding, rather than 'its always there' is the best way i can describe it. So its less likely to be a case of low supply, just your breasts 'knowing' what and when they are needed.
Keep feeding, drink enough, rest if you can (at least stop and put your feet up!) and if you are concerned about supply for a while, feed a little more frequently if you can to stimulate the supply.
alex