Not sure of what is this

Hi, it isn't easy for me to ask for any kind of advice on this. I'm a very shy person, always have been like this, depending in the environment I'm at the moment or the people that are around, . I was bullied throughout Highschool and it had a great impact in my social interaction skills as a kid back then because in a small town like mine, most other children were involved in the situation, it got me to a point where I barely got to talk with other children and preferred to speak with adults. However, over time this thing got to a point where I didn't even want to laugh at other people's jokes because I felt extreme discomfort. I'd always try my best to avoid crowds because I'd get pretty paranoic, thought they would all be talking bad things about me or laughing at me. So, I eventually grew up and graduated highschool, I recently passed to my second year as a med student , had difficulty socializing in my first semester but now things are going at their own pace. I'm pretty concerned about the fact that I used to worry about lots of things in the past and get really sad over long periods of time, but now I still worry about many things and realised I started getting physical symptoms like poor appetite, abnormal sleeping patterns, cramps whenever an important activity is due. does anyone know What could it be? Also, I noticed that I get blue when I'm not under pressure. Thank you so much if you got to read this whole thing, any advice is greatly appreciated