Good evening. First please allow me to say how sorry I am that you are going through such a difficult period in your life as a result of this man. Based on what you have identified in your question it sounds though this started off as feelings of grief and loss. A lot of people attribute loss to someone passing away but the pain of losing someone such as in your case can be just as painful, if not more so.
I notice that you are already on an antidepressant which is very good. Following up on what I mentioned above that this likely started off as a loss response...it's probably turned into a depressive episode which likely prompted your physician to start you on the citalopram...which is a very good medication and in case they didn't explain it to you...it takes approximately 6 weeks for it to build up an effective level in your blood to start working.
Having said that, what will truly benefit you in helping you work through this difficult period in your life would be for you to see a therapist. Preferably one who is experienced in Cognitive Behavioral Therapy as this helps you to identify the impact that your thoughts have on your emotional state and where they can lead you to...which is often a negative state. I would also like to suggest a workbook based on the same theoretical approach which includes exercises that you can do in the interim period until you see a therapist. Please find below the link to the workbook.
I sincerely hope this has helped and please feel free to ask any additional questions or if you need clarification on any of the suggestions I've offered.
Please let me know if you have any further questions that I can help in answering for you.If you feel that I've answered your question to your satisfaction then I would greatly appreciate your clicking the ACCEPT button thereby giving me credit for the answer and suggestions I've provided to you. I hope this finds you well and look forward to your response.
I can certainly appreciate the pain you are experiencing,,,both professionally as I've seen it in my own clients and even personally. The best thing you can do for yourself at this point would be to strongly consider seeing a therapist to help you through this difficult period in your life.
Please let me know if there is anything further I can help you with. If you feel I have answered your question to your satisfaction and to the best of my ability then I would sincerely appreciate your clicking the accept button thereby giving me credit for helping...but only if you feel it's warranted. Thank you for the opportunity to help you and I wish you the very best!