“Should I see a psychologist if I can't get over my ex?”

I believe you should. If it's a case of not being able to over an ex I would ask if what way might it be affecting your life. for example, this would include being depressed, anxious, abusing drugs or alcohol, being less productive, or other ways it is interfering with everyday functioning. The emotional pain of loss and grief are common after break-ups. However, if it's a case of being protracted (lasting too long) I would recommend that you consult with a therapist.

Yes that would be a good idea

Yes. All life transitions may warrant a story of a psychologist. You are going through a grief moment after a loss of a loved one, a loss of the ideal future you designed for you both, etc. A psychologist can help you.

Therapy may be helpful.

Take a peak at this link...
https://www.vox.com/first-person/2017/1/3/13938008/breakup-strategies-research
or
https://www.huffpost.com/entry/science-backed-ways-to-get-over-ex_n_5783cdb8e4b0c590f7ea4886

If these don't help see a psychologist who is experienced at helping heal breakups

In a word, YES. That applies to other perceived losses or disruptions in the course of your life. It can be an ex-anything: a job, a career, a parent, a fortune, a child, a reputation, an ability or skill, etc. Often, in such situations, is energizing you to do something to undo the loss, either by retrieving what has been lost or do something in the past to cause it not to have happened. The first is often impossible, or impossible for you, and the second is always impossible, but the unconscious mind hasn't gotten the news, perhaps because accept that it happened. Help is available, and getting some can prevent a lot of suffering and lost happy time.
I hope this is helpful.

Dr. T. Kimper