How would I know if I am wearing all-heavy armor?

The description will tell you if the item is heavy or light armour. Refer to the image below. (The small, dark grey text just above and to the left of the item name)

It depends entirely on the materials used.

These are all the materials that are considered heavy:

• Iron
• Imperial
• Steel
• Steel Plate
• Falmer
• Ancient Nord
• Dwarven
• Orcish
• Ebony
• Daedric
• Dragonplate

Conversely, here are all the light armor types:

• Hide Armor
• Imperial Light Armor
• Studded Armor
• Leather Armor
• Thieves Guild Armor
• Dark Brotherhood Armor
• Nightingale Armor
• Elven Armor
• Scaled Armor
• Glass Armor
• Forsworn Armor
• Stormcloak Armor (Officer Armor as well)
• Dragon Armor (Dragonscale version only)

You can also check by examining the armor from your inventory. It'll say heavy or light.