Sue, some pictures might help. Showing the full frontal of the house and a bit closer of where they appear to have dropped.
If this is a sudden occurrence, and you say the wall is bowing out from the house, I think you may need a structural surveyor to inspect pretty sharpish. Are you having any structural work done on your house?
This is going back 30 years but a friend who is an architect once told me that (terrace) houses were often built on foundations (of sorts) but that the bays were just sort of stuck on. This meant that over time, the building and bay moved independently.
It was common in 1900 (& in the 1930's) to build bays with less substantial foundations than the foundations of the main house behind the bay. ie two foundations with two different loadings.
This could lead to whats called Differential Settlement - it can slowly start within 15 to 20 yrs of new build, & can occasionally present as bulging - although, as above suggested, bulging might better be associated with weak replacement Pvc frames.
Are there any signs of cracks or surface disruption inside the main house?
There are also other possibilities for what you describe.
Why not post pics showing the whole bay from the front, and pics showing the bay from the LH side and the RH side?
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