Is koikokoro 恋心 a proper japanese word, if yes what exactly does it mean?

Question:

Answer:

I regard it as ”One's romance”　more personal feelings for someone（e.g. My romance, Her romance）
恋心 is widely used for the title (incl. Japanese translation) of love songs from Tango to Japanese Enka.

-------- edit:
※There's a difference between 愛 and 恋
恋心 --> 恋する気持ち、恋をしている心　loving someone in one's heart
a WRITTEN word, used in titles/lyrics/poems as mentioned above.
-------------
"koigokoro" is not really used colloquialy