Stress can play a huge role in cortisol production and weight loss stall/weight gain so I would say yes, absolutely. Hang in there, try to sleep well, and find ways to deal with your grief. I am so sorry about you mom. :( As time goes on, you should start seeing weight loss again.
The process of grieving is a slow one: there are 5 stages which the mind will work through in good time. You also need to take care of yourself physically - body and mind work together. Your loss of a loved one also means that your stress levels are high. Try to take it easy for the next 6 months or so, there will be good and not so good days. There are support groups out there which can easy your pain. We are so sorry about your sad loss - take care of yourself!
The side effects of allergy medications keep some people from using them. Natural remedies can be a great alternative, but some are more effective than others.