Having a deadline can be stressful, you will need to make sure you do/did your best to achieve it. However; the people that support you (your boss) will need to make sure that you can achieve this as well. That is their job.
That can be done by throwing yourself at the work (if you have the confidence that you can actually finish it), but sometimes the best result is that you remind people of the agreements made when starting the project.
If the agreement or understanding is that there will be 3 people working on the project, then your boss cannot reasonably expect you to finish on your own within the same timeframe.
If you have practical concerns (I cannot achieve X within time or by my self), then state that to your boss, and expect to be helped with it. In scrum terms this would be called an 'impediment'.
If you are not sure were you're standing, ask your boss for assistance in validating it / determining what remains to be done, and give your estimate if it is possible to do so.
And on a personal note: chin up, take a deep breath, give it your best effort and try to have some fun while you're at it.