My 3 month old son has never slept thru the night. He's BF and for the most of the first three months he ate every 3 hours thru the night. He did however grow 5 inches and 6 pounds during that time - so he has been on a major growth spurt since birth I think

We have a very consistent bedtime routine of BF, bath, and then I only have to hold him for about 5 minutes and he gets very heavy eyes. He goes down most nights still slightly awake in his crib in his own room (usually around 8:30). I then usually dream feed him around 11:00pm without any real problems. When he wakes for his feeds, he usually eats and goes right back to sleep.
A few weeks ago, I started to try to stretch the time at night atleast by and hour or two. When he would wake up I would go into his room, leave him in his crib, give him his paci and shush him for a few minutes. It seemed to work some - he would stay asleep until about 3:30 or 4:00. I would feed him and he would sleep again until 7:00-7:30. This wasn't perfect, but I was atleast feeling human.
This week, he has started again waking up about 1:00AM and will not easily resettle. I try, and he rests for about 10 minutes at a time. I re-settle him repeatedly utnil about 2:30 AM until I just decide to feed him - thinking maybe he his really hungry. He then sleeps until 5:00 ish and I repeat above until about 6:15-6:30 when I go ahead and feed him. He then will sleep until about 8:00.
He has been swaddles almost the whole 3 months - he wouldn't sleep not swaddled. But during this last week, he was getting one of his legs out of the swaddle blanket. When I would go into his rrom, he was just kicking and kicking his legs. I thought maybe that he was trying to free himself from the swaddle, and in the process waking himself up. So for the past 2 nights, I have just put him to sleep in his sleep sack. He has been going to sleep fine, but waking around 2 and 5 again - with his legs just out of control kicking. It is more than just a little jolt, etc.. that babies do during their sleep. And I don't leave him crying in his room very long.
Any ideas??? SHoudl I just keep feeding him when he wakes and then put him back to sleep? It is almost easier, but I have really been trying not to establish any bad habits. I would like to stretch his nightime sleeps out for everybody!!! I don't want him to get into the habit of eating every three hours forever

And any idea on the lefg thrashing about? I could reswaddle him, but it didn't seem any more successful than the last few nights when I have been leaving him unswaddles.
Sorry for the long post. Any advice is appreciated! I am starting to get really exhausted, and feel like I barely have the energy to be a good mom during the daytime. Also, I am supposed to be going back to work just 2 days a week starting in March - I don't know how I am going to be able to concentrate and be productive.