Hard to really say much without knowing exactly what ALL you were wearing when you were cold.
But, at those temps, if you were cold, I would start with a good quality, good-fitting, 7mm wetsuit. Note: "good quality". A low quality wetsuit is not as warm as a high quality one. Also, a poor-fitting high quality wetsuit is still not warm.
Add a hood, 7mm boots, and gloves.
If that is still not warm enough. change the hood for a hooded vest worn over the 7mm wetsuit.
If that is still not warm enough, but you don't want to get a drysuit, try a semi-dry suit like a Hollis Neotek.