@Rudals Did the jacket feel tight and restrictive under your armpits? The shoulder width looks fine and I'm guessing that this issue is caused by the armhole being to tight to accommodate the width of your upper arm and possibly also being too tight in your chest. This also would explain why it's only on the right side assuming that is your dominant arm. I could be completely off since I'm only trying to tell by looking at one picture, but this is probably one of the most common problems I have had personally with RTW. The fact that the SA tried to recommend you a 38 when the 40 clearly looks to tight should explain exactly how you ended up in the predicament you are in to begin with.
Fact is, I believe Monkeyface has pointed this out, my weight gain has contributed to fat buildup in my chest and tummy. I just need to get rid of this....honey moon fat.