Perhaps, there is the need to find company of a Shaykh whom you can learn from and take spiritual advice in order to discipline your nafs/self and progressively advance in both your akhirah and dunyah.
So make appropriate duas such as; Ya Allah I need to overcome my problems in life to be successful please help me every step of the way because I am weak, please bring such an esteemed teacher who succeeded on the righteous path whose blessed company I can truly benefit from and whom can elevate my soul and strengthen it by pure association, your love and sacred knowledge.
AND, supplicate with His 99 names for help and strength. https://99namesofallah.name/
Consider this carefully: someone abused their position over you and destroyed your reputation, yes I agree it's a horrible situation to be in. However, reality is there have been many who had worse than this; there are those who have lost property and loved ones because of standing up for the truth, there are those who are in jail for the rest of their lives/ a very long time due to proclaiming the truth. And, we want to get into Jannah? Then we ask ourselves what have I done to deserve reaching there. Shall I be stuck in my darken worrisome place giving up or shall I keep striving on because Jannah is really worth it.
And, if you can put the incident behind and move then this is one great victory for you that will no doubt strengthen your emaan significantly. And, another if you can scarifice for your studies to become a doctor then you would be able to assist both Muslims and non-Muslims. A very notable position done for the right reasons. So, maybe can delay marriage until then because you will also be more ready.
The Istikhara prayer has certain conditions to be fulfilled and one of those is that a person must be halal for you and if wanting to make nikah, both should be ready in all/most aspects so that the union would be really blessed and your children benefit.
Should medicine not be your passion then you can try something else and discuss with your parents. There are many great options. Also, there are many Muslimahs in various fields including medicine, so you never really know, be greatful to Allah saving you from the unforseen harms. A door that closed probably was not best for you and there are many many more. Have faith!
Also in Islam, there is no obeying to anyone who calls towards disobedience . So, teach your mom/family about what Islam states regards marrying a non-Muslim, in fact were you already teaching your family more about Islam they would have been more supportive and encouraging with the right goals for you. It doesn't happen overnight but takes time and dedication like every other successes.
May Allah help you, make things easier and grant success. Ameen.