I am so sorry about your daughter. It breaks my heart to hear you went through such a horrible tragedy. My condolences to you.
Before you explore a psychological cause for your trouble swallowing, I highly recommend you get another medical opinion. It is never a bad idea to be sure and rule out any physical cause and sometimes doctors can be wrong.
If you are cleared medically, then you may be having symptoms of anxiety. Although it is not common, sometimes anxiety can cause your neck muscles to tense and make it difficult to swallow. Psychology theorists suggest that it is related to the difficulty of "taking in" something unpleasant or even something traumatizing. And if you feel that is accurate for you, then you may want to talk with a therapist.
Did you have therapy at any time after your daughter's death? If so, then you may just have a recurrence of feelings related to the trauma. Sometimes, things we see or hear can affect us unconsciously and we start feeling anxious or depressed, without really understanding the cause.
If you did not have therapy after your daughter's death, then your symptoms most likely are related. It could be from unresolved feelings or a reminder of the trauma.
To find a therapist, try asking your doctor for a referral. Or, if you attend church, your pastor can be a good source either for therapy or to refer you. You can also search on line at www.find-a-therapist.com.
If you feel that you want help right away, especially given how much weight you have lost, you may want to ask your doctor for an anti anxiety medication to help take the edge off the symptoms. Ask for a mild medication, just something you can take until you start seeing a therapist and begin to address the issue.
I hope this has helped you,