I'm amazed at the responses here. I also can't believe people are questioning why the op is tired if her DH is doing the night feeds. When ds1 was 6wks, he was only ever off the breast for an absolute maximum of 1 hour day or night. He was generally on for 45mins-1h then off for 45mins to 1h. I was on my knees with exhaustion. He also would never ever be put down or nap for more than 20mins at a time and only ever on top of me. So even if DH has done the night feeds, I would still have been wiped out.
With my first, I did all the night feeds as I struggled to express. It was fucking hideous. When pg with ds2, I was still BF so I weaned ds1 and started to pump and freeze for the baby. This meant lots of stored milk for ds2 meaning DH could do night feeds until about 12wks when my body had recovered. DH himself thought this was more than reasonable.
Oh and with my 3rd, I went straight back to work and that was massively easier even though ds3 was still waking in the night.
Last point is that if you don't have anyone else you can meet up with or see in the day, the loneliness can be crippling. Despite popular perception, baby groups aren't always the easiest place to make friends esp as some can already have a cliquey group who don't make an effort to speak to you. I felt incredibly lonely as all my friends still worked full time and although both my mother and MIL were still alive at that point, both worked long hours in their own professional careers. At 6wks, if I could have changed my mind, I probably would have done. By 16wks, I loved him more than life. As Mr Lennon said, 'whatever gets you thru the night, is alright.'