Hi there - your little man is about to hit upon his first milestone, which can throw any routine out of the window - his 6 week growth spurt! So more frequent nightwakings and needing to nurse more are common at this age, however there are things you can do to help him (and you!) through it.
Firstly, I would start to cluster feed him at night - you are trying to get as many calories as possible into him to 'tank him up' so that he will start sleeping longer at night - and carry on with the DF. In addition to this, swaddling is very useful at this age as is mastering the art of pat/shush to get him to sleep. There are some great links at the top of this board on how to do pat/shush with babies under 3 months and also instructions on the aussie swaddle.
Hang on in there, I can remember how exhausting those first few weeks are, but they do get better...honest!
Dee
x