Here is the full list of all 14 Lovey-Dovey Lockdown achievements.
Start a new game
Unlock Sex 01
Unlock Sex 02
Unlock Sex 03
Unlock Sex 04
Unlock Sex 05
Unlock Sex 06
Unlock Sex 07
Unlock Sex 08
Unlock Sex 09
Unlock Sex 10
Unlock Sex 11
Unlock Sex 12
Clear game with the perfect ending