Hi Jen, I have twins, combination BF and formula til they were 13months. I had to stop partly due to returning to work but also as DS just stopped wanting to BF. It really upset me at the time, I had so wanted to continue, having spent so long trying to establish BF in the first place, to then have DS just reject me felt awful, and awful for DD who was still enjoying her morning BF. I still look at DD and feel a tinge of sadness that I didn't get a bit longer BF her, but that was how it was to be.
anyway I cut down a feed every week til I was down to one and then DS stopped anyway. I had spent so long worrying that if I missed feeds I would lose supply and dry up. Well it's been 4.5months and I am still producing milk! I squeeze a tiny bit out from time to time and am always surprised when I see the milk come out! I had thought about restarting but I know that it's not the right thing for me and my babies. You will have no issues BF, while DD wants to you can continue at the feeds that suit you and her, when the time comes and she wants to stop she will let you know as my DS did. Stop when you are ready, for work you can just cut down to the feeds that suit you both. On the twin website I go to a mum there said it was like her body knew that she worked three days as on those days she didn't BF but the other days she did and always had enough milk, so maybe for you on your days off you can feed as normal?
Are you hoping to have anymore children? If not do you think you are feeling down because you know this is the last time you get to BF/have a little baby etc? That was an issue for me, knowing that although I would desperately want another baby that realistically (financially) I won't be having any more, so when I stopped BF I felt a bit like it was the end of something special that I won't ever get to experience again.
Sorry for rambling, good luck with however it all goes and returning to work!
IUI Nov 09 BFN ..... 1st ICSI Oct 10 BFP m/c 8weeks

..... 2nd ICSI June 11
MY DIARY
Valentine's day twins 2012
And a surprise DS 27/1/15