Hi Sally, the constructions with the verb "manquer" are always a source of confusion because they are the other way around in French as in English.

English: I miss you. -- "I" is the subject and "you" is the direct object.
French: Tu me manques. -- "Tu" is the subject and "me" is the indirect object. (You are lacking from me).

Say it a hundred times and use it frequently. After a while it starts to sink in.

-- Chris (not a native speaker).