I'm not sure I understand what you mean by "use" the discs? Are you wondering whether you can install the expansions you own physically despite having the rest of the game digitally on Origin?
If that is what you're asking, you can. I'd recommend registering your physical copies through Origin. Doing this will give you digital copies of all the physical expansions you add. So they'll all be on Origin and easy to install all at once.
To add them, you open Origin and go to your game library. There, you'll see in the upper right corner "(+) Add A Game," then "Redeem Product Code." A dialogue box should open with a spot to type the CD Key. Put the CD Key in, add it, and repeat this for all of your physical copies.