It's a long one that WW. We are in the sunny phase afterwards (21 weeks) but sleep is still a bit hit and miss. I persist with day sleeps and try to get him to have at least 3 if not 4. As NIcnac says distraction really starts to kick in now, it's such a lovely age in many ways with new challenges . I try and get one longer sleep for him by feeding at the afternoon wake up and if he's sleepy he'll pop back to sleep in my arms if I cuddle him. I find a comfy spot on the couch if DD is asleep and try and have a nap myself. I've also tried to get a bit sleep for myself by occasionally expressing and DH does the first wake up feed so I can get a block. I didn't do this with DD but its working this time around if I can be bothered to express. I also find after a bad night I can hand DS over to DH early in the morning after a feed and put earplugs in and get another 1-2 hours before he starts work. Perhaps that's an option?
Would DH be comfortable with just you cosleeping with DD and he sleep on a mattress or couch do you can get some more zzzs?
Hang in there Saffy, this too shall pass, hopefully you can get some zzzs for yourself and DD will settle into the next phase.
I recommend getting a copy of the WW book either through your library or Internet. A godsend when you're at the end if your tether and in a WW.