K.
I know this is going to be tough but my Dr recommended it for my children. At 3 months they should be sleeping through the night and there is no reason that a baby needs to get up during the night(mostly just habit). So let your baby cry during the night feedings...I know sounds mean but works. You will sleep and baby will sleep after a few nights but wow what a relief. For you I would make sure its quiet,no caffeine an hour before bedtime,and maybe read or watch a bit of tv before going to bed.