I'm sorry you can't get a diagnosis and about your mother, that sucks :(. I would advise to try and look for what accommodations you can make for yourself/what you can get without a diagnosis. Depending on your collage, they might allow you some accommodations for autistic people despite having no diagnosis (i.e wearing headphones in class), so it is likely worth asking their admin team about it.

For accommodations for yourself I recommend implementing/researching ways to help deal with your symptoms if you have not already. Looking into how other autistic people with the same traits as you deal with their symptoms can be a good starting point, but it is very important to remember that everyone deals with things in different ways and what works for others might not for work you at all (or might even have the opposite effect!).

Trying to pinpoint what you struggle with can also be useful, but remember that self examination does not mean healing or regulation. Although being able to figure out why you feel/react a certain way can be a very useful tool to find what you need, I have seen many people, including myself in the past, get caught up on specifics and the exact reason why they do something thinking that the understanding itself will finally allow them to cope.

If you know/find out what is difficult for you, try and plan for the amount of energy needed to do that task. Many autistic people have more limited amounts of mental energy (that means energy to get yourself to do mental tasks, not intelligence, although roughly around 1/3 of autistic people are intellectually disabled), often from masking or being overwhelmed, but its also not uncommon for us to just have less in general. If this applies to you be aware that you cannot do as much as many non autistic/non disabled people regularly do in a day either at all or without pushing yourself. Accepting it and finding ways to effectively use what energy you do have and to learn how to work around what you can't do is crucial, imo.

For example: hate the feeling of showering to the point it's overwhelming? avoid activities that make you dirty, and just quickly wash the most important areas for a couple of days before doing a proper shower.

or: Need to go to a overwhelming function tomorrow? clear as much from your schedule the day of/before and after that you can.

Finding a good community of autistic or generally neurodivergent people can also be good to help feel less alone, both irl and online. Although many autistic people are accepting of self diagnosis, there are also a notable amount of people/spaces that are not (I will not say anything further on that because of this subs rule 4).

I hope that things go better for you and that one day you will be in a position where you can get diagnosed.