I'm so sorry for your loss. Losing a child must be one of the hardest experiences.
The 'firsts' are always extremely hard but try to take it slow - one day at a time. If you can, try to remember the positive holiday times you had with Jason. It might be painful but in time those memories become treasured parts of holiday periods. Even maybe consider a different ritual or activity that can become part of your holiday celebrations to remember and honour Jason. It's a way of keeping him with your during the holidays.
Is there anyone you can talk to about what you are feeling? Sometimes it can help to try and lean on someone else and be able to vent. If not, please rely on the forum for a while. There are a lot of people here who are willing to listen and support you as much as we can. Please feel free to PM me any time if you want to talk.