I went through the same thing with my own daughter at 3 1/2 months. She was sleeping roughly 10-5, got the cold, and well that was that. It was up to eat every 2-3 hours pretty much every night. Absolutely exhausting. I totally totally empathize with you.
I do not know how you feel about sleep training. I have read every sleep book I could get my hands on: Weissbluth, Ferber, Sears, Karp, Pantley, and several others. I even read one called "Sleep Talk" that basically advocated hypnotic talks while your kids sleep to get them to sleep more/better (yes, I was that desperate). They all have their own sleep philosophies and methods that range from letting the baby cry until sleep occurs (regardless of how long that takes) to letting the baby sleep with you and feed as needed. The Pantley book, "The No-Cry Sleep Solution" had some good suggestions, so I wanted to share it with you. I also just got a new one from the library called "The Lull-A-Baby Sleep Plan." I'm not sure what it proposes, but I wanted to share the title.
Basically there are several factors to consider:
1) how does your daughter fall asleep for the night? Do you put her in the crib and she goes down or do you have to nurse her and/or rock her to sleep? I rocked my daughter to sleep every night for the first 7 months until we realized that she went down faster and easier with my husband. You might try having your husband put her down while you stay quietly away.
2) Could you and your husband trade off night feedings? That way, at least there would be a little more sleep for you two.
3) Where does your daughter sleep? Have you considered cosleeping or do you want her to stay in her own crib/room? Some babies are more soothed with cosleeping and others just get up more because the food is always available.
4) If you and your husband sleep in the same room as your daughter have you considered sleeping somewhere else at least for the start of the night? Have you considered moving her crib into her own room or vice versa? Even then, you might want to stay out of the room for the first part of the night. I would regularly fall asleep on the couch while my husband went up with the baby, and I would just join them for the first feeding and then on. I had heard that babies can smell breastmilk and so I thought that by removing myself, I would at least try to prolong the interval until the first feeding. Sometimes it worked, and sometimes it didn't
5) Finally, it sounds like she could need a little more milk at bedtime and elsewhere, so it might be a growth spurt. Also, she might be teething a little early. So you might want to check for signs of teething, and if so give her a little Tylenol. Or try giving her a little more food (but I do know that breastfed babies will only eat what they will eat). Alternately, if you're not averse to it, you could try a little formula at the last awake feed (It's supposed to make babies sleep longer). However, don't listen to anyone who tells you that if you give your daughter solids/cereal, she will sleep more. That has not been shown to work at all.
6) Have you tried putting her to bed earlier? That worked a few times for us.
7) Does her diaper really need changing during the night? You might try a heavier diaper (or an overnight one) to avoid changing her, which might make her wake more.
8) Finally, how easygoing is your daughter? If she is easygoing, sleep training will definitely be easier than if she is somewhat more wired.
As you can probably tell, I have tried just about everything. My own daughter (now 18 moths old) was/is very stubborn. Well, determined. She has always refused all bottles, pacifiers, and all pumped breastmilk. She also resisted all methods of cry-it-out, so I abandoned the method. I am a grad student, so I was able to be with her, but it is still exhausting. After her cold my daughter refused her crib. We ended up buying a cosleeper but basically she slept in bed with us for several months because it just got too darn exhausting to have to get up and feed her every 3 hours. I would just turn over, feed her, and go back to sleep. However, I really didn't like doing it (I like my space!), so we have been steadily working my daughter back into her own crib. However, it has not been a short or easy process. For the last several months my daughter has gone down in her crib and sleeps there for about 8 hours until she wakes for a short feed and then sleeps for another 4 hours. We have also recently moved her out of our room. Soon, soon, we hope to have her sleeping for 10-12 straight hours.
I am sorry this is so long, but I have been there. Seriously, I really really empathize with you. Hang in there, follow your gut, and do what works for you and your family.
Hope you sleep better soon!