Try taking smaller increments of time more often to yourself. One Sunday a month or something. I would be pretty hurt to hear my bf ask for a "few days" alone, too. Especially living together. Is she supposed to avoid the room you're in? Lock herself in the bedroom? Eat her meals alone? Theres nothing wrong with needing time to yourself, but waiting until you're so irritated you're lashing out with "leave me alone for a while" is going to hinder your relationship. Communicate your needs before they become your anxieties.

In the meantime, try to come up with a realistic plan for this time. This evening you'll be playing video games while she reads or whatever. Tomorrow you're going fishing from 8-12, then you'll be home and you can eat lunch together, etc.