Sleep deprived! Need Advice on sleep training!

I really hope some veteran mommies out there can help me!!! For the first month my son would go down around 11 and wake up 3-4 hours then every two hours until about 9. The last two and a half months have been hell!! (He's 3 1/2 months) it's like a rodeo to get him to sleep every night. We have had a nightly routine since birth. We swaddle because he is like a bucking bronco and its the only thing that calms him. He goes down around 9-10 (the process starts at 830!) then he is up every hour to two hours. It takes almost an hour to get him back down at that. I plan on starting the Ferber method this Monday. He does well with going down for naps. I lay him down half asleep and he self soothes pretty well, but only sleeps a half hour at a time about 4 times a day which doesn't seem like enough sleep, but he's not crankey so I guess it's enough. Any advice on how you got your babies to sleep longer periods at a time would be greatly appreciated!! I know it's going to be hard, but it has to happen for the good of both of us!!