You can clear your professions by re-typing in the command that set them. Ex: /sk (skill) select main/second/bonus
Otherwise, with no professions you can go up to a max in adequate with every skill as a non-human, with one profession it knocks them all to clumsy and a second causes them to all go down to inept. To reset main and second professions refer to the above. Any professions chosen will have the adequate max lifted to the max of Aengulic on the professions chosen, allowing you to do better within that craft and allowing you to continue training the skill through the nexus crafting plugin. Selecting a profession will drop the skill of anything not that profession due to the max of each skill being dropped, and the one being raised. (I believe this is what you were referring to when you went to set your mining as your secondary, but the skill was lost due to you already choosing a main skill and your secondary was set to clumsy in the process.)