It means “I love you so fucking much but I know you probably don’t love me back” is usually used to tell someone you like them without actually telling them.
Ashlyn: ilysfmbikypdlmb
Kayden: but I know you love me <3
Ilybikydlmbaihmboi, is an acronym for: I love you but I know you don't love me back and I hate my body over it.
When a girl is texting a boy that she has unrequited feelings for but she wants to be complicated asf she'll send, ilybikydlmbaihmboi to express her feelings yet confuse the shit outta him.