Insecure Uke

Daiji na Koto nano de, Nido.

I know others, but Daiji na Koto nano de, Nido. is exactly what you're looking for.

Others include:
Usagi Otoko Tora Otoko
Darling
Dog Style
Heaven's Love
Sick
Ore wa Senpai no Nan Nandesu ka!?
Neko Mata
Mou Ichido, Nandodemo.
Kowagaranaide, Soba ni Ite
Manazashi no Hayagane
Kono Ore ga Omae nanka Suki na Wakenai (He generally seems confident, but is actually pretty insecure)
Doushitemo Furetakunai (This also really fits what you're looking for)
Soredemo, Yasashii Koi wo Suru (Spinoff of previous)
Ashita mo Tanin

Thank you so much! ヾ(☆▽☆)