What is the ruling on frequently swearing oaths, making vows, and supplicating against oneself for قطع الرزق (severing of provision) due to severe obsessive-compulsive disorder (OCD) in prayer and ablution?

The cure for obsessive thoughts (waswas) is to ignore and repel them, without needing to make oaths or vows, and to continue with acts of worship without paying them any mind. As for oaths and vows made under the influence of waswas, there is nothing (no consequence) in them. But for what was done by your own choice, expiation (kaffarah) is required.