Getting a diagnosis

Hi, I'm a 20 year old female from Wales and in the last two to three years I have been leaning more and more into the likelihood that I am autistic. BUT I have no idea what to do. I can't speak to my family about it as last time I did they were dead set on the fact that I'm not as I don't show the same signs as my brother (though my mother did once tell me that she thought I may have had it when I was younger but she wasn't sure if I was just copying his behaviour or not. I wasn't, I didn't hang around him a lot as he had really bad anger issues). I've been thinking about this for a long time, stressing myself out and getting anxious over the fact that maybe this is just all in my head or it's not as bad(?) as I'm making it out to be.

I only made up my mind to get some help with this a few days ago as I was reading a book written online and the author (an autistic female) wrote the character to be autistic and have the same mannerisms/traits as her. The further on I went the more I kept thinking 'I act exactly like this' or 'I do these things all the time'. I contacted the author and told her about my experiences, what behavioural symptoms I have etc and she told me they're the same things that she goes through too. 

Basically, I have a ton of behavioural symptoms that I wasn't aware were common (for women).

And I have no idea what to do.

I don't want to tell my family that I want to get diagnosed as I don't think they'll be supportive about it but I'm also really stuck as I have no idea how to go about getting one.

I was wondering if someone could give me some advice on what to do in terms of getting diagnosed. Who do I speak to?

This has been stressing me out for a long time but it's worse now more than ever as I'm in university (and I'm already struggling) and I have deadlines coming up and I just feel like it's getting a bit much. I don't really have anyone to talk to about this...

I'd appreciate any advice you can give.