How do you write my sweet love in Latin?

"My sweet love" in Latin is dulcis amor meus (regardless of the sex of the person you're talking about).

Strictly speaking, if you're addressing someone as "my sweet love," you should use the vocative form of the adjective meus, which is mi (the vocative forms of dulcis and amor are dulcis and amor). For example, Richard Maidstone's Concordia, a poem written in 1392, refers to King Richard II as "mi rex, mi dulcis amor" ("my king, my sweet love"). But there are examples with meus as well, including the Latin hymn Jesu dulcis amor meus.