“I can't stop thinking about my ex”

What could be going on

Grief (complicated, disenfranchised, anticipatory): Breakups are real losses; check whether you've let yourself feel the loss.

Limerence: Fits if it's intrusive, you replay moments and feel a high from any contact or sign.

Rumination and worry: Check whether you're going round in circles about why it ended.

Trauma bonding: Fits if the relationship had cycles of hurt and relief that made you more attached.

Anxious-preoccupied attachment: Check whether breakups generally hit you hard and lingeringly.

Replays conversations for days: Check whether you replay conversations for days or weeks.

Also said as

• it's been months and I still think about her every day
• how do I stop obsessing over my ex
• I check his instagram constantly
• I can't get over my breakup
• I'm still obsessed with my ex
• my ex is on my mind all the time