When there's someone too smelly in the same room as me I sometimes feel sick.
There's one unbelievably smelly person who always rides the same train as me, and when they're (standing/sitting) close to me I sometimes feel nauseous.
Mさん、こんばんは。
大変ですよね。満員電車で色々な苦労がありますよね。臭い人は多分自分が臭いことさえ知らないのも多いと思います。
「同じ部屋の人が臭すぎてたまに吐き気がする」＝
"When there's someone too smelly in the same room as me I sometimes feel sick."
「いつも同じ電車に乗ってる人でとてつもなく臭い人がいて、その人と近くになった場合、たまに吐きそうになる」
"There's one unbelievably smelly person who always rides the same train as me, and when they're (standing/sitting) close to me I sometimes feel nauseous."
臭すぎて = too smelly
とてつもなく臭い = unbelievably smelly
吐き気がする・吐きそうになる ＝ feel nauseous; feel sick
ご参考になれば幸いです。
There's a guy who always gets on the same train as I do and he's really stinky. Sometimes he stands/sits close to me and when he does I almost feel like gagging.
この場合、次のような言い方ができますよ。
ーThere's a guy who always gets on the same train as I do and he's really stinky. Sometimes he stands/sits close to me and when he does I almost feel like gagging.
「私と同じ電車に乗る男性がいるんだけど、その人すごく臭いんだよね。時々、私の近くに立つと/座ると、吐きそうになる」
almost feel like gagging で「吐きそうになる」と言えます。
ご参考まで！
アメリカ合衆国 
カナダ 
