The ornamental design for a supportivepillow, as shown and as described.
FIG. 1 is a left side perspective view of a supportive pillow showing my new design;
FIG. 2 is a left view thereof;
FIG. 3 is a right view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is another left side perspective view of the supportive pillow in accordance with my new design shown with a person's head laying on the supportive pillow.
The broken lines included in FIG. 8 of the supportive pillow illustrate environmental structure and form no part of the claimed design. The remainder of the broken lines shown in the Figures represent portions of the supportive pillow that form no part of the claimed design.