Hi Wisna. Good to hear the gas is improving a little.
I really wouldn't worry about rocking and carrying to sleep at this point. Don't feel at all pressured to rush in getting your LO into the cot for naps, although the BWing books explain how to set up the EASY routine and begin independent sleep early on there are very many parents who don't begin with their babies so young. Tracy's books show us how BWing can be started at any point either because a parent hasn't come across the techniques until later on, or because they choose to do something else first. It's fine.
In fact the general feeling on the forums is that sleep training is rarely tackled until later, and the general feeling I get reading posts here is that very few start so young. I'm one of those few, I read BW when DS was around 4 weeks old, some of the methods and good habits that were detailed I was already doing and the rest of it just made sense to me but even so I walked, cuddled and rocked my LO to sleep (or very almost to sleep) most of the time and gradually over a few more weeks made moves to get him in his cot just prior to sleep. I rocked his cot too...not a BW method...but we achieved independent sleep.
So, I just want you to know you are not alone and no one here will frown upon you in any way because you are loving, cuddling, rocking and helping your little baby to get some good sleep.
Over the next few weeks you might feel you are able to put him down as he gets drowsy - or not. Whatever you choose to do know that the community of parents here is always here to support.
One thing I will say, if/when you decide to make some changes and introduce him to sleeping in his cot, PU/PD is a last resort method, usually reserved for older babies. I wouldn't advise it for starting out sleep training with a 3 month old, shush/pat (or adapted) is much gentler. In any case shush/pat is used with PU/PD when that method is used, so you'd still use it.
There are lots of other boards on the site, including the birth clubs, you might find them useful.
xx