Any reason a muscle relaxer (baclofen) would ever cause or contribute to pain as opposed to help reduce it. sometimes it feels like my back almost hurts less when i'm late on a dose?

It is common for some pain medications to actually increase pain due to how nerve pathways work. This can be seen with narcotics. While baclofen is a muscle relaxer and not an opioid, similar issues can happen when managing pain with almost any medication. If your pain is less when late on a dose, I would consider reviewing your diagnosis and approach with your doc. May be time to lower or stop it