How to make friends

My whole life ive never had a lot of friends, but I would have a couple 'outcast' friends. Then in 8th grade something sort of traumatising happened and I havent seemed to make friends since. Luckly my younger sister can make friends and her friends are okay with me tagging along (despite the 6+ year age gap), but I kind of want to make my own friends again.

I dont know how to though. There are people who I want to be friends with but I just seem to accept that I cant be friends with them. 

Theres this one boy in my chemistry class though, Jordan, and I really want to be friends with him. Most people if they try to talk to me, talk in a baby voice and just do small talk, and then they make fun of me later. Some are more obvious than others. But Jordan talks to me the same way he talks to anyone else, and he doesnt talk to me because im the quiet kid but because im just someone he can talk to lol. Everybody else gets annoyed by Jordan (hes got ADHD) and sort of make fun of him (including the teacher), but I think hes very interesting to listen to and his non-neurotypical-ness is very nice to be around when the rest of the day im having to constantly make sure im doing everything right and trying to decode their behaviors. 

Ive tried to talk to him once. We were lab partners one day and he was talking about fire and plasma or something. I tried to say something but then my voice went weird and I dont even think I formed words. He was just quiet for a moment (probably trying to figure out what I just said) and then he just went back to his ramble. 

Today he came in the classroom and said "Wheres Mr (teachers name)?" and nobody in the class even looked up at him. One kid says "Jordan, just shut up". But then I looked at Jordan and shrugged (because I didnt know where the teacher was), then Jordan just laughed and said "shrug" but not in a mean way. He then started talking to me and smiling and wanting me to respond. I wanted to say something but my mouth just wouldnt work.

I struggle talking but especially if its been over half a year, how am I just supposed to go from never talking to being his friend? Or not even friend, but how do I just talk to him?