All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah, and that Muhammad (may Allah exalt his mention) is His Slave and Messenger.
As for your supplication against yourself, you have to repent from it. The Prophet said: "Do not supplicate against yourselves, do not supplicate against your children, do not supplicate against your wealth, lest that coincides with a time when Allah is asked and He grants, so He answers your prayer." [Muslim]
You should supplicate Allah for yourself with all that is good, for Allah hears the supplications. As for your doubt about the vow, then you are not required to do anything because in principle a vow doesn't happen unless its condition is fulfilled.
Regarding the sign you mentioned, you should ignore it as no ruling can be based on it, but you must expel these negative thoughts and work hard to lead positive life and focus on your studies, and look for what benefits your religion and your life.
Allah knows best.