When you decrease is it only one row or do you decrease in every row
I am not sure what pattern you are using but according to a pattern by redheart you should be decreasing each row. Could you provide a link or a name of the pattern you are using?
Since this blanket is a rectangle, your directions may have you decreasing at different rates on each eadge. The pattern of decreases should be similar to the pattern of increases at the beginning of the blanket.
Can you tell us where you are in the pattern and maybe quote a row or two that are causing the problem? Don’t scan or quote the whole pattern because that raises copyright problems.
11 colour 6 pink 9 len 21 colour then when I get to row 52 am 3 stitches out