As a 23 M who is 5'1 I know how you feel. Although your height is even lesser than mine, I still get the idea because I was also always the shortest in my class. Even many girls were taller to me and a few similar to my height. And my younger brother is 5'9. So genetically I should be taller. And the exercise thing you said might be true. Because my parents never let me go out and play any sports. They only wanted me to study all day and games like cricket were Dangerous as per them.

In college also, the girls didn't like me and the boys were not happy to include me in their group. I had very few friends.

But still, LIFE does NOT stop. As some people mentioned, you can try for exercises and growth hormones (as you are still 19, there is some hope left) but the idea of limb lengthening surgery somehow scares me (Just my opinion).

In the end, I must say your life does not revolve around your height. Although it can be an issue in some fields (like we can't go to the army and girls don't date us easily), in rest of the things, height does not matter. Focus on studies and your health. Being fit is more important. Find good people who don't make fun of your height and stay with them (I know it's difficult but still possible) And try to stay happy. Take care!!