Johnny :
You'd probably start to get scared real quick because he'd just look at you without saying anything for about a minute. He can't help it because he literally just imagined the rest of his life with you and this new addition he just found out about. Johnny would totally all of a sudden just lift you up and spin you around after coming back to reality and then treat you as even more than a queen. (if that's even possible.
Lucas :
Lucas would blast through the roof if it were possible. Although if you are in a low ceiling place while telling him this he may hit his head from jumping with excitement so be careful about that. He'd then proceed to find the nearest window to yell out of and tell the whole world that the most beautiful woman is having his baby. Oof you're so lucky.
Jungwoo :
I think Jungwoo would melt because his heart is on fire with all the love he suddenly feels. He wouldn't be physically excited much but he'd hug you right away. I'm not sure if he'd cry much but like I said he just feels so much love for you and his baby that he'd never take you or them for granted. He'd also be cute and say thank you already for carrying his baby. Guys this is a lot of fluff I don't know if I can live to write Ten's reaction.
Ten :
He would have hearts and stars in his eyes after hearing you're pregnant. Honestly he wouldn't know what to do with himself and would be so excited thinking about everything to come. I feel like after you telling him this he'd definitely make an effort to be around more and would always remind you of how lucky he is to have you.