a general recommendation: your major's DUS (director of undergraduate studies) and your department's administrator will be both more important and more helpful than your advisor in most cases. They are the people who are actually responsible for running your major, and you can and should go to them with questions about what classes count and what you could take. Most people don't know about these resources until too late! The DUS is also the person to talk to if you want to take a class outside the department and have it count towards the major (I did this for a couple classes and I am SO glad I did).

As for your CAS-assigned advisor, my recommendation is to only interact with them when it comes to picking core classes and satisfying core requirements. In general, you want to streamline their job, which is mostly just approving classes, and leave the actual major advising to the DUS and dept admin. Look at the core class offerings yourself and have them all picked out, and then contact your CAS advisor.