In English, the phrase "maza tujhya khup khup prem ahe ani te kadich marnar nahi" roughly translates to:
"I love you very, very much, and will never stop loving you."
It seems like your ex-boyfriend expressed his feelings of deep love and affection for you on your birthday, emphasizing that his love for you is strong and enduring. The statement also includes the reassurance that he will never stop loving you.