Hi There J.,
If you are breastfeeding your baby, you might find that attending a Local La Leche League meeting to be a help with nightime parenting. Go to www.lalecheleague.org to find a meeting near you.
It is completely normal for a breastfed baby to need to wake at night to nurse. It is completely normal that a breastfed baby will sleep through the night at two months, but not at 31/2 months because you are heading towards the big 4 month growth spurt. Almost all breastfed babies still need to nurse at least once at night.
As babies head toward 4 months they are also beginning their teething. It may be months before you see or feel a tooth, but if you are seeing a lot of drool, the baby's shirts are wet, and there is a little rash on the chin or neck then teeth are most certainly coming.
If you are expressing breast milk, why not nurse the baby at night? Just like many adults awaken in the middle of the night to have a drink of water or use the bathroom, so do children as they grow and develop. Children do nothing but change and grow for years and sometimes it can keep them fussy and wakeful at night. For years!
You can create for yourself quiet and thoughful nighttime routine that includes nursing and rocking a wakeful baby back to sleep. If you also include a snack for yourself, you will wake up in the morning feeling better.
Nightime Parenting is a challenge, Dr. William Sears has written a good book about it.
Research has shown that too much time in baby seats and car seats can cause developmental delays, as children just don't get enough room to stretch and move around. Give your baby as much "rug time" and snuggle time as possible during the day and the baby might sleep better at night.
Hang in there, the next six months are the most delightful time with a baby.
C.