J.
Hi J.! I think you are completely normal at 3 months postpartum, especially with 5 others needing your time as well. Physically, your body has alot of repairs and emotionally you are going in many directions. And, most importantly, your body is programmed hormonally to be attentive the every, frequent need of your new baby above all else. It's a beautiful thing. It is a difficult thing.
I have 2 kids (nursed the 1st and I am nursing the second) and with both, I had to "get in the mood" in what seemed like a robotic way for the first 6 months. That was after a C-Section and then a vaginal. We had KY gel next to the bed where'd we go and invariably we were interrupted. I saw it as a gift for him. For me, it wasn't fair to him to make him wait 6 months until I was fully ready. So as long as it wasn't every other day that he was wanting to be intimate, I was ok with letting it happen. And, yes there were times that I delayed it a day or so for any number of reasons. It seemed that each time we would, I felt a little more back to normal in some way and I would make sure that I emphasized that little bit of healing to him. A reminder to him that this wasn't a permanent state. On my husband's side, he new it wasn't real easy for me and so he was real tender and gentle both physically and emotionally about it all. So, it turned out to be a way for him to show me his love in it all.
Even now that I've healed and all is back to normal, it is hard to not be interrupted so it has become a joke for us and has added some spontaneity and lightness to our relationship in an unexpected way.
Personally, at 3 months postpartum, I think it is absolutely normal and necessary that you are always mom first. You are programmed for that. I see the question as, in what ways can you give to your marriage even when you can't 100%. One thing that I always reminded myself was that it wasn't a permanent situation and that with time all would cycle back.
Best of luck, congratulations on your baby and on choosing to noursish him/her with your milk.