Your question reminded me of my own situation during my PhD. I share with you my experience and hope you can relate to it, and maybe learn something. I was also in third year, physics PhD, with published papers and lot of presentations at conferences. But still I was constantly thinking about quitting. The thing which made me to think like that, now I look back, was not actually the research or academic component, but was the environment and the situation I was in, and the relation with my advisor. Plus some exhaustion due to lot of work I did in 2 and half years. I had a strange relationship with my advisor. I was depressed for sure, tried student counselling, doctors, tried to make friends ... and at one point I was thinking of even committing suicide, believe me it is true. The next day I called the helpline and told them that I was suicidal. These type of thoughts never came to my mind before or after that. People almost stopped talking to me, if they talked they talked with strange reactions. I was lucky enough that there were couple of colleagues, to whom I could talk normally. I was not in my home country, and it was really hard to make contacts outside the work. There were some racial people around also, doing subtle racial comments now and then, intentionally or unintentionally, I don't know. All these little factors contributed and made me think to quit. The amazing part was that it was the research which kept me engaged and interested, and I kept pushing forward. Deep down inside I was damn determined that I have to finish and finish as early as possible, because if I do it late, I am going to get medically ill for sure. So I made a plan. I started writing my thesis without telling anyone. I showed my stuff to my thesis committee and couple of other professors. I talked to an emeritus professor who was serving as kind of a student counselor. Before my next committee meeting I made a nice draft and submitted to the committee before the meeting. I convinced the committee that I can write my thesis and they recommended to submit in the next six months. This time I did not listen to my advisor who was suggesting otherwise. I did additional work, edited my thesis carefully, and submitted. Arranged my defense. My defense was extremely hard. One of the member in the panel was a great researcher, senior most professor of our institute, and was often very hard when it came to scientific discussions. Hard in the sense that he was a brilliant thinker with enormous experience, and was well known worldwide for his contributions, very dedicated, very bold when it came to criticism, but enjoyable if you like to fight. I stood my ground. Finally I passed. Easy said than done.
My advice for you is the following. If you have even a tiny bit of hope that you can finish on the basis of your work, go for it like it is a war, and you have to defeat the enemy with great valour. Its a battle for your 2.5 years of work with great publications, which is at least 3% of your life span, and you do not get the life twice. DO NOT give a second thought. You are going to get so much respect for yourself, whether you stay in academia or not. Remember -- your work is going to decide if you are going to get a PhD, not your supervisor, feed this to your mind and fight for it. Fight for it like its your territory and you are invaded. Believe me you can succeed.
There is a very subtle stage in this process. I believe that a PhD student starts thinking quitting when there is no external approval of the work which the student has done. Such a student does all the work but thinks that nobody cares about it. The
truth is that actually NOBODY cares about it. You have to care about it and you HAVE TO follow your gut feeling when you think that you are ready to finish. Nobody is going to tell you. And that's where the student is most confused. In addition, when student decides on it, there come stages like convincing people, editing your thesis again and again and again, and fixing a date to which all the members agree to. These are loopholes and take dedication to get through.
Finally, if you have a medical condition, be very very careful. DO NOT take more stress no matter what happens. If needed, compromise with your research output a little bit, there is nothing wrong in it. If you take more stress in such a condition, it can affect your upcoming life. Take care of yourself. Slow down. Meditate. Exercise. There are ways you can get through this. Recognize what helps you and what causes problems for you. Avoid the latter. Don't be afraid of people judging you, you are here for yourself. Again, I stress that be very careful if you have a medical condition.
I did not quit, and so I can not relate to such a situation. Consider taking into account suggestions from people who already took the decision of quitting.
One more thing, I tried almost all the options you mentioned for help -- therapy, taking break etc, they surely help but the effect is local in time. I suggest you take the challenge head on, and use these methods as your support system. Again, if you have medical condition you have to be more careful.
Best wishes.
