I thought that wind may be stopping him from sleeping any longer- getting 5 hours stretch on a good day, 3 hours on a bad day. Difficult to get baby back to sleep and baby been restless in cot and keeping me awake.
Wondering how much longer I can go on and be this sleep deprived.
He's sixteen weeks and he did manage to do a 6 hour 45 min stretch
ONCE at around weeks.
So I made a concerted effort to wind him. More burping than usual, holding upright when b feeding (as much as poss). Holding upright after feeding, being upright as much as poss during the day. Some leg cycling before bed.
Two big feeds before bed and a bit of burping...
And Hey Presto- he slept for 6 1/2 hours!
Problem is I didn't. Couldn't sleep and kept waking in the night! 
Ah well, I am hoping this is not a coincidence or a one off, fingers crossed!