Personal pronouns like "my" are used less frequently in Czech than they are in English, that is why I translated "hello my sweetheart" as "Ahoj miláčku", without the "můj". The phrase "jak jsi se měl" is written in standard Czech, you can also use the colloquial "jak ses měl".
In case you cannot see the Czech marks above the characters, they are:
accent (short slanted line) above the "a" in "miláčku"
little v-shaped sign above the "c" in "miláčku" and "e" in "měl"