does anyone know a manga that shows many different sex positions?

hmm maybe try:
http://www.mangago.zone/read-manga/kuroneko_kareshi_no_asobikata/
http://www.mangago.zone/read-manga/i_want_to_be_naughty/ (the whole warui series)
http://www.mangago.zone/read-manga/hidoku_shinaide/
http://www.mangago.zone/read-manga/himegoto_asobi/
http://www.mangago.zone/read-manga/stay_gold_koi_no_lesson_a_to_z/
all yaoi btw.

i am also looking for what you're looking for,i found it by mistake but when i start reading it i rlly liked it,but sadly i forgot it's titles,but i was hoping to find it