I know it's another long sleep post but I really need help! :(

Hi again ladies...as a few of you know I've posted a few times on here regarding DS's sleep but I really need some support...
To go back to the beginning, DS was born 13 and a half weeks ago a healthy 4.02kg. From birth until around 7 weeks he was an angel sleepwise...waking only once in the night to feed and sleeping beautifully, swaddled in his bassinet with his sleepy sheep white noise. At around 9 weeks, which I'm sure was developmental, he started to shorten his day naps to around 30 mins which was frustrating but at least he was still sleeping well at night. However by 10 weeks this lack of daytime sleep started impacting his night sleep and he was starting to wake a few times and needed to be picked up to go back to sleep. We also introduced a dummy fairly early as he was and still is a sucky baby. By 11 weeks not only was his night sleep getting worse, but so was his feeding as he was clearly overtired and pulling off the breast. We thought reflux at one point as he gurges quite alot and tried some meds on a paed's advice but soon realised this wasn't it and took him off them. I had to express and feed him some bottles which I did to up my supply and also tide him over and make sure he was eating when not feeding at the breast properly. Luckily he doesn't seem to have a preference for a bottle and switches between both quite well (now back on breast about 95% of the time and is feeding better). At exactly 12 weeks to the day we decided to go visit Cecile. She got us to try doing the 20/5/20 for one nap a day (20 mins with him patting down, dummy etc but not picking up or talking or making eye contact, 5 mins leave the room and then 20 mins more of the previous). That night he did an amazing night (with no intervention) and slept 7.15 to 3am, fed and slept until 7am and we thought hey...maybe he's working this out himself...but no, I think that was just a one off bday present to himself! So that day we tried the 20/5/20 and he didn't cry and fell asleep by the 2nd 20 mins and had a good nap and we thought, wow this is fab. Next day, not so fab, he cried the entire time but ended up falling asleep towards the end. Next day again the same. Over the week this has improved, he doesn't cry as much and tends to just fight but started falling asleep in the first 20 mins. Yesterday he actually fell asleep almost immediately. So daytime is improving slowly. Night is another matter though. We moved onto just patting him down and giving the dummy instead of picking him up which was working however he was still waking just as often (every hour or even less). At the same time we decided to try and put him in a sleeping bag rather than swaddle him in case this was annoying him. No real change. After speaking to Cecile again she is now advising leaving him to cry for 20 mins at every waking through the night which just doesn't feel right to me as he is only 13.5 weeks old. She basically is saying that the patting down isn't working as he is waking just as often and we need to move on and that if we don't it will only get worse! :( She also said you can try smaller intervals of leaving him to cry but that it will take longer and smaller intervals only teaches him to cry and expect you to come. When I asked if 20 mins was not the same she said well if doesn't work at 20 mins you then have to move to 30 or even 45 mins which is something I know I could never do, not at this age anyway. So yesterday my hubby, MIL who is here from the UK and I all talked it through (thank god for MIL who has been sharing the night shift with me so I at least get half a nights sleep although she leaves in a week!!) and we thought no we can't let him cry, we'll just keep trying to pat him down in the hopes it will get better. Then last night was the worst ever - he was waking every 20-30 to sometimes 45-60 mins in the first half of the night (MIL shift poor thing) until around 1.30 when he was actually hungry. Every waking you could see he wanted to sleep but just kept jerking around. So after I fed him I abandoned the sleeping bag and reswaddled him and he then slept 2 hours, and after waking again at 4 and it taking almost 45 mins of patting and shushing and not picking up he then slept through until 6.10am. So one decision has been made, I am going to start swaddling again to see whether that will help as not sure if the fact it's getting worse is because we put him in a bag and he keeps waking himself up....OR that if in fact Cecile is right in saying if we continue doing what we're doing it is only going to get worse...
Would love some advice and support from you lovely ladies..sorry for the long post but I really don't know what to do and I'm just not comfortable letting him cry. He is the loveliest, happiest baby always smiling and talking and I don't want that to change. We waited such a long time to have him so I don't want to do any damage to him emotionally or anything like that by letting him cry but at the same time we cant go on as we are...Please tell me some of you have been here and that it DOES get better, not worse as Cecile is saying it might!! :(