Lately, i've had stools that have ridges on the top and almost appear to be square or rectangle in shape. i have had hemerrhoids in the past. could they be related?

Sounds OK: You might be having some recurrence of your hemorrhoids. Stool shape really varies quite a bit and would not be diagnostic of hemorrhoids.

Probabaly fine: You are probably just fine. However, because a real discussion can't be held on these forums, the safest thing to do is discuss with your primary care doc or a specialist for these systems, who can sit and discuss the full story with you.

Shape of stool: By itself is not indication of anything serious. But a simple rectal examination would reveal any abnormalities that might be causing it. Go and see a doctor to make sure that you don't have anything close to the anal opening or any occult blood in the stool.