you will most likely need to advocate for yourself a lot, which can be extremely exhausting and hard to do when you're autistic. You might even need to go and get a second opinion if you don't get a diagnosis. Also depending on your agab or what gender you are, this can make it even more difficult- if you're a woman (trans or cis) or even just assigned female at birth regardless of what your gender is now, you are less likely to get diagnosed. The reason for this is because of lack of research in regards to autistic women & females, as well as misogyny in the medical field- it also can have to do with the fact that if you're raised as female, you might have had more social expectations and you learned to mask because of that.
Masking is definitely something you should look into, because a lot of doctors will see how good you are at masking and take that as a sign of you not being autistic (which is stupid imo)... For example, if you're able to make eye contact but all of the other traits/symptoms of autism apply to you....they might deny you a diagnosis just based on that.
Do your research on who's in your area, check reviews, see if anyone specializes in autism or are an autistic dr them self (i got diagnosed by an autistic dr and i believe that's why the process was so much easier for me compared to others), things like that.
A lot of medical professionals will deny you diagnosis' for things that you show all the signs of, they will even write down in your report that you displayed symptoms but refuse to give you a diagnosis anyways. Keep in mind that not every medical professional is an expert in specific conditions, which is why finding a specialist might be helpful. It would probably be helpful for you to write down all the symptoms & to write out which ones apply to you and how.
Also, when you're tested, some of the questions can be worded in a confusing way, so if you're able to i would ask for help if you don't understand a question. There's also specific tests for autism diagnosis' sometimes, so if you're going in for a general eval & don't know if they have it, it would be good to let them know beforehand that you want to be tested specifically for that, too.
If they refuse to let you take the test, that's an issue with them and you might need to find somewhere else to go because it's unlikely those types of people will give you a diagnosis, let alone consider you for one.
overall, it can be incredibly stressful to go through this process, just make sure to document any mistreatment you might face and to remember that you know yourself better than anyone else!