One more thought.
I say all of the following because these are things I have learned from many years of dealing with people and relationships of all kinds. I didn't think this way when I was young. but this is knowledge I have gained.
This is rare. But it can happen this way: If you tell someone calmly and respectfully that you can see how hard it may be for them to believe you or to be supportive, that your inability to be what they want can be disappointing to them, and you are not saying they are a bad person or anything, but if they cannot change how they are reacting to you and accept you and support you for how you are, you will have to choose to take care of yourself and not have them in your life any longer...........that person might think again about how they are treating you, and might even change.
As I say, it's rare and shouldn't ever be something you expect because 95% of the time that will lead to disappointment. But if you think someone genuinely cares for you, it is worth a try.
Having been there and done that, I will offer another word of advice, though. Often a person will say they will "try". That's fine if they really do, and you can see evidence of that effort. But if genuine change is not seen within a few months at the most, they are not trying, but rather using that statement as a way to continue as just they have been. Don't keep giving them "another chance" over and over, because if you do it will go on forever. This, of course, applies to any form of mistreatment or lack of respect.
The thing to remember is that it is a mistake to think that if someone truly cares for you they will understand, and/or be supportive. This just doesn't prove to be true.
There are many kinds of people and many kinds of caring, and not all of them are selfless by any means, and not all are the same. Everyone loves or cares in their own way. For some people this is selfless, for others it is self-serving, and there are many variations in between.
Some people are capable of things that others are not. There is not only one way to care for or to love another person, and it's unwise to expect that everyone sees caring for another as you do or can love the way you do.
If someone says, "if they love you they will....(fill in the blank)" what they are really saying is that if they love you the same way I do, they will.... Which may not be helpful if the person you are talking about is very different from the one saying that to you. Maybe if YOU love someone, you will always do your best to be understanding and supportive no matter what, but not everyone else loves or is capable of loving or expressing that love in the same way you do. And if they don't express it in the same way it doesn't mean they don't care.
Again.....we are all different in our capabilities and ways of caring and abilities to show that in different ways.
Just because someone understands and is kind doesn't mean they truly care for you and just because someone refuses to believe you or is not understanding or supportive doesn't mean they don't care for you. It can mean that, for certain. But equally it can mean something else, and have to do with what that person is capable of rather than having to do with you or how they feel about you. It might even have nothing to do with you at all, but be due to what is inside that person.
For some people, the best they can do is to care for you in a self centered way. For some people the best they can do is care for you but not be able to get to the point of understanding enough to be the kind of supportive friend or family member or partner you need.
None of these things mean that the person who is unsupportive is necessarily a bad person or doesn't care about you. It just means that for whatever reason they are not helpful to you, not supportive, or in the worst case they are toxic to you. If this is the case, you have to choose whether you will allow that person to continue to hurt you, or take care of yourself. There's no inherently right or wrong choice. There can be and often are many factors that go into making such a decision. It is not always just a simple thing and it can be excruciatingly hard or complicated depending on your circumstances and what the relationship is.
But there is always a choice, and if you make the choice to keep a toxic relationship, it is good to do so with your eyes wide open and knowing what you are doing and why. Knowing that you are choosing to do something harmful to yourself. And if you make that choice, then accept that decision and also choose not to complain about it, because at that point complaining about it will only add to the hurt it is already causing you by making you feel like a victim. Rather, find ways to work with it, to empower yourself and to protect and take care of yourself the very best you can within the situation you have chosen.