My spouse needs time alone. Is that a sign they don't love me?

Not necessarily; some people genuinely need time alone to recharge, and that is not a rejection of you. Introverted people recharge by being alone, just as others recharge by socialising. Do not read it as a sign that they are bored or drifting away. Discuss each other's needs: how much time alone they need, and how much time together you hope for. Find a balance that respects both, for example giving them a little space after work before a long chat. Trust grows when each other's needs are understood. See communication & emotions.