Depressed PhD student in USA, wanting to quit
Help is very likely available. Consider contacting a neutral group at your university. Such groups typically include:


the omsbuds office/ ombudsman
the PHD student's association
the student government
counseling services
international students services
the graduate school


Your own university may have different groups.  Try some google searches, such as "(university name) help graduate student neutral". Start the conversation by stating you are looking for advice and alternatives to your present situation. Up front, specifically ask which parts of the conversation are confidential, or not. Usually, for example, anything involving physical harm requires the person you speak with to report. 

When meeting, put together a short narrative that frames your problem. Consider in advance what you want, and what your questions are. Also be open to options of which you have not thought. Realize that most of these groups will be more likely to give advice on how to move to a more tenable situation than they are to wade in and fix the problems that exist. Some may, however, offer to facilitate discussions, and advise you on how to negotiate.

Finally, realize that the university has a stake in your success. Within reason, they will likely work to make things right.