So, if you are a Warlock 4/ Paladin 2/ Sorcerer 2:
You have 2 Warlock Spells you can cast per short rest. Both Spells can be cast as 2nd level spells.
You cast your other spells as a 3rd level caster meaning four (4) 1st level slots and two (2) second level slots. Plus two sorcery points...