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A picture of this pattern would really help. If there isn't a link to the pattern, perhaps you could post one
It looks as though you change to stockinette stitch for the upper part of the coat. Is that what the picture shows? Decrease on rows 2, 6, 10, 14, 18 etc. Those decreases must occur along the length of the row, not just at the edges as is usual. I would mark the decreases on the first decrease row with a stitch marker and then use that as a guide for subsequent decreases (work 2 fewer sts between decreases on subsequest rows). The markers can be a simple as a circle of contrasting yarn.
Is there someplace else in the pattern that you've had to decrease, other than as part of the pattern stitch?