My DS was sleeping about 7 hours a night until he had his second jabs after which he started waking up every couple of hours. After about a week of this I went to stay with my SIL for a break and during that time he went back to sleeping through. However on my return home he has once again started waking in the night going from one waking, to four wakings over the period of a few days.
A lot of people keep telling me he must be hungry and I need to start weaning him but he is only 16 weeks. I don't know what is going on with him though - he has always slept at least six hours straight - now I am lucky if I get two.