are there any yaoi manga where one of them is shopping for condoms or toys and get caught? or like the other boy works as the cashier?

Does arenting a porn video count?
Trash-talking, Sadistic Me is Taken by a Dull Salaryman

Sorry I am new to this and not very good yet. Are there any yaoi manga where the uke is heartbroken and has low self esteem from getting rejected then he gets together with another guy.

Hello 😀
It's best to start a new thread for a new question or request instead of posting in an unrelated thread 🙂
Here are some that hopefully fill your requirement.
Koe shika mienai
Daiji na Koto na Node, Nido.
Soredemo Mata Asa ga Kute Koiwosuru
Shiawase ni narunosa!
Ouji no kikan (3rd story)
Koi to wa yobenai
Last train elegy (ch5) from shuuden elegy
Sagatte omachi kudasai
Senpai
Konbini-kun (not rejection by bullying)
Ai da no koi da no first story