I am I my early 20's and I think I may have undiagnosed autism. I have always found it really hard to make friends and meet new people. However, it has been noticed that I tend to quickly form relationships with autistic people and find it easier to communicate with them than other people do. I often feel anxious around new people and there are only ever a select few who I can be 'myself' around. I become very irritated with normal things such as needing to message people back constantly unless I am wanting to talk to them/about something specific and I find it very difficult to hang out with more than one friend at a time. I can become very attached to people and have an overwhelming need to know that they are safe but I don't deal with such behaviour in return. I tend to get upset easily, not always knowing why and I rarely understand sarcasm and think that people are just being mean.
Could this be autism? I have taken a few quizzes and I got 32 in the last one and it said to think about seeing a doctor if you scored over 31...
The most appropriate way to ascertain if you are on the spectrum would be to research the features and traits and decide if they apply to you.
Here is more information.
Here describes the diagnosis process.
All the best.