My 12 week-old is waking a lot at night. We've been handling nap issues as well, but during the night she used to go six hours regularly, even 7 and 8 hour stretches and now, consistently, wakes every 3 hours, if not sooner. She goes to bed at 7:00 (with a consistent bedtime routine), wakes at 10:30, 1:30, 4:00, 5:30 and then I can hardly get her to fall back to sleep. At 7:00 (or 8:00, depending on whether she sleeps again) I get her up for the day. This, when she used to just wake for the 4:00 feed, then sleep till 8:00. She's had this new pattern for over a week
When she wakes I feed her, she takes half to a full feed.
At first I thought it was a growth spurt, but after so many days, I'm afraid it's settling into a pattern. Also, I've posted about transitioning to a 4-hour EASY but I don't really think she's there yet.
I don't really know how to handle his. Here are my questions:
1. I'm afraid that if I try to calm her without feeding her through the night she'll go hungry, but if I do feed her at one of the wakings won't that confuse her at all

2. How on earth can I get her to sleep between 4 and 7/8

? I've tried shh/pat and although she does stop crying she doesn't fall asleep, no matter how long I keep patting. I've also tried pressure on her body to prevent the jolt but I can't get her past the 20 min. mark, she wakes.
3. Why is she waking so often, and is there anything I can do during the day to help her sleep better?
Some info that might help you: she doesn't use a paci (she sucks on her thumb) and we don't swaddle (I don't even know how to say it in my language ..., should I introduce this now

). Dh is of no help, poor guy, because he cannot stand to hear her cry.
Any advice welcome. I'm really tired from the lack of sleep, plus running around with big sister, etc.
TIA,
Sara