Light entering from sides of blackout curtain
We have this issue in both kids bedrooms that face west.

What I did was, below the blackout curtains, fix a blackout roller-blind against the window, and add thin strips of wood down the sides which the roller-blinds fit underneath, this stops all light bleed at the edges, and because the blind comes right down to the bottom of the casement, it stops bleed from the bottom as well, which seems to be your main issue.

Or, you could also look at adding black blackout material to the back of your curtains, which will drastically reduce the reflected light bleed (but increase the amount of heat radiated into the room - having a secondary blind helps with this, as well)