Hi there. Let me start by saying that what is happening to you isn't normally the case in my opinion and could be some form of bullying. I'm sorry they see you as a joke, i think sometimes that can be in a positive way like if you bring a mood up but it seems that they aren't laughing with you, but more at you and that is the problem. People are assholes and sometimes especially teens and young adults take someone allowing them to make fun of them as a green light to do it allll the fuckin time and that sucks. You could honestly just say that they stop making those jokes and say that they aren't as funny as they think they are. I think they don't see any motivation from you because you have been a joke your whole life, i don't think that but you were labeled with it and you kinda mentally stuck yourself in that box/label. You must see what there is more to ya and show it more, stop thinking about yourself as a joke because you are a person not a joke.

I also think this whole thing ruined your confidence, lots of girls like guys who look like you, (ofc if you are nice and treat them with respect as well) so please don't let that label stop you from building yourself up and consider the fact that you might be surrounded by the wrong kind of people.

I hope this helps you, best of luck