Is your product going according to plan? 6 months by yourself without releasing is a very long time without feedback or validation of any sort. That kind of uncertainty can wear you down.
Is it possible to release a cut now? Actually meet people or customers for feedback before going further?
On the other hand, if it is not going as per plan, may be it is time to let go. Try to tell to yourself it does not matter anymore and spend a few days away from screens and keyboard. Sleep well and eat healthy. Once you are well rested, go out and meet friends or strangers, who will not remind you of your project. Take as long as you want as mental and physical well being is so much more important than a startup. At the end of the break, you will be able to decide what direction to take.
It could also be that you have a more lucrative/interesting idea on mind and the current project is a blocker. That can make your current project feel more and more like a dead weight around your neck. In such case, you will need to decide what your priorities are and pivot accordingly.
Sometimes, just doing some market research to validate the need for your product can also do wonders to your morale.
If none of these help, pl consult a professional. Do not be afraid. Burnout, just like any other symptoms of illness, is just another indication that for the time being, we need to bring our focus back to us, in our life.