Say happy birthday/no

Hey everyone can u give me advice. Im 16 and 4 months ago i broke up and the one who initiated it was him because he said we didnt match he didnt like me being angry. The breakup is rough for me even until now. We are in diff schools and now im in diff country. I last communicated him when he told me he want to breakup and then i blocked him. I suffer some sort of guilty because i think i made him miserable because of the relationship. Because of this breakup my self esteem becomes lower. I believe in God and i dont know whether deleting his contacts pleases God i am so confuse and then i ask a senior in my church he said i should build a good relationship with everyone so i should contact him to reconciliate and then be friends. But its so hard i planned to greet him happy birthday but when i heard from my friend that he has got a gf it comes to my mind that he is happy now he doesnt need me anymore he has replaced me idk what to do i was in tears and my senior said its ok if u cant it will take time to get over it completely. Guys what should i do is greeting ur ex happy bday neccessary ? I feel way comfortable having no more connection with someone who hurt me badly even until now it still aches but he did say when he broke up with me he still wanted to be friends but i dont want to be his friend