Help me figure out this lotion/sunscreen issue?

My dermatologist says I must start wearing sunscreen all the time. Until now I’ve only used moisturizer with sunscreen on my face unless I know I’m going to be out in the sun a lot and then I slather on the sunscreen and wear clothes that cover most of my body. And I always wear a hat.

I’m have freckles and moles and my grandmother had to have multiple melanomas removed and that is why my dermatologist is concerned.

Now, I live in a dry climate and I have problems with dry skin. I apply lotion many times a day. Sunscreen is hardly moisturizing. If I have to wear sunscreen everyday, even when I’m in my car, office and house most of the day, do I apply lotion then sunscreen or the other way around? If I reapply lotion do I need to reapply sunscreen? Even at the end of the day when I’ll be getting in my car and going home?

Also, my office has skylights.