What to do

I joined this forum because I have recently begun to suspect that I am autistic and I am trying to determine with some level of certainty whether this is the case. I know I could express my concerns to a health professional and try to get a referral for diagnosis, but I fear being wrong for some reason I can't properly articulate. I have no real frame of reference for autism so I could be completely wrong. Anyway, I am trying to learn more about the experiences of others and about what constitutes ASD before I do anything. I will provide a brief introduction of myself, and if anyone has advice about my situation, I am open to it.

I am a female in my early twenties and I am in the last year of my undergraduate degree. I am a double major in biology and mathematics, and I plan to go to graduate school to study biology. Biology has been my single-minded passion since childhood and I only realized in college that my passion for my subject is unusual. 

I have always struggled with socializing and social anxiety, because I don't like that the thoughts and actions of other people are out of my control. I have also had a difficult time understanding subtext and body language, and I miss subtle cues during conversations. I have a hard time controlling my body language and expressions when I am not focusing on them, and people have said that I often seem angry. I have gotten better at these things over time, but it takes conscious effort to act and to interpret the behavior of others properly. 

I also have sensory issues, but I don't know if they are at a level of severity dictating autism. I am easily startled by sound, touch, and movement, and I don't seem to adapt to repeated stimuli. I am also very particular about what I wear in terms of texture and fit, and it causes me distress to wear certain things. Being sweaty or damp from rain really bothers me, so much so that I have left class or work to change or dry off. these kinds of things make me feel overwhelmed, and I generally can't focus until they are resolved. I also have tactile habits that I am constantly doing, such as picking or rubbing or tapping on things. This is especially prominent when I am nervous or overwhelmed, and I frequently damage the skin of my hands and around my nails at these times by scratching or picking. I also scratch at my scalp.

I absolutely do not handle change well. I don't know precisely how to define my experiences during times of change, but I don't feel like myself and small things set me off. It is especially difficult for me when my family moves, or when I do something or go somewhere I have never experienced before. I have tried not to let it limit my actions, so I ignore it and do things anyway. For example, going to college was extremely difficult for me because it was an entirely new situation, but I did it anyway despite being under a great deal of stress. This stress led to issues with depression during my senior year of high school.

At this point, it is probably clear that I have divided my introduction roughly by diagnostic category, and that I don't have a good grasp of the word "brief". This concludes my introduction, and if anyone has advice on my symptoms or seeking a diagnosis, I would be pleased to hear it. In particular, I am trying to reach a threshold of certainty at which I am confident enough to go to a doctor (though I'm not certain such a threshold exists).