Just Got Over My Ex

Ended with Alex last week after three years. We were living together but drifted apart over the summer. Now I'm struggling to get back into my old routine, strange dreams and waking up feeling like something's missing. Is it weird that sometimes, even now, when I'm alone, I still feel this... pull? Like there’s a part of me waiting for him to come through the door? Should I be trying harder to move on, or is it normal to linger like this after such a long relationship?