anyone has a list of yaoi with weak or sickly characters? =D

FF

I didn't know specifically what you were looking for, so I gathered a wide range of manga that deals with mental and physical disabilities, as well as diseases.

Bl:
Germaphobe: http://www.mangago.me/read-manga/ten_count/
Afraid of the dark: http://www.mangago.me/read-manga/kizudarake_no_hakoniwa/
Withdrawal Syndrome: http://www.mangago.me/read-manga/hana_to_usagi/
No facial expression/bad at talking: http://www.mangago.me/read-manga/bukiyou_na_silent/
Social Anxiety: http://www.mangago.me/read-manga/konbini_kun/
The seme keeps getting physically injured: http://www.mangago.me/read-manga/oita_ga_sugiru_wa_koneko_chan/
Magic illness??: http://www.mangago.me/read-manga/the_priests_chart/
Deaf: http://www.mangago.me/read-manga/sign_language/?av=5
Narcolepsy: http://www.mangago.me/read-manga/the_strange_story_of_a_guy_next_door_and_a_novelist/
Deaf/other disabilities: http://www.mangago.me/read-manga/hidamari_ga_kikoeru/
Blind: http://www.mangago.me/read-manga/love_is_blind_kitano_megumi/
The uke is constantly sick because his vampire bf sucks his blood i guess??: http://www.mangago.me/read-manga/dalkomhan_namja/?av=1
2 disabled mc's: http://www.mangago.me/read-manga/nanohana_boys/


Non bl (just in case something seems interesting to you):
The mc deals with lots of different illnesses during her journey across Japan as an adventurer: http://www.mangago.me/read-manga/fushigi_no_kuni_no_bird/
Autistic son and various other characters who have developmental issues: http://www.mangago.me/read-manga/with_the_light/
A spirit suffers from a sort of magical disease where he needs to be purified: http://www.mangago.me/read-manga/mitsuyokon_tsukumogami_no_yomegoryou/
Pregnancy/all the medical stuff with that: http://www.mangago.me/read-manga/teen_mom/
mc is in and out of the hospital: http://www.mangago.me/read-manga/jewelry_hane_to_kotori_no_subarashiki_hibi/
mc is trans, undergoes sex reassignment surgery: http://www.mangago.me/read-manga/umareru_seibetsu_wo_machigaeta/
Blind mc, other mc is deaf: http://www.mangago.me/read-manga/can_t_see_can_t_hear_but_love/


Non bl where the mc deals with sick people as a healer:
http://www.mangago.me/read-manga/jui_san_no_oshigoto_in_isekai/
http://www.mangago.me/read-manga/colette_wa_shinu_koto_ni_shita/
http://www.mangago.me/read-manga/tenju_no_kuni/


I hope you find something interesting. Happy reading! (●'◡'●)ﾉ