Hi
Últimately he couldn't be loyal to you and now a legal step you can initiate is a police complaint of promise of marriage and not keeping it.
A case of rape can be also charged if police helps you but since the relationship was with consensus it will free him off charges in the trial or during the investigation.
Your feeling of hurt, cheat ed and abuse is not understood by law under the specific provisions other than what I mentioned in the beginning
Ge tan FIR under IPC for promise of marriage and having relationship on that promise. If there was an incident of you medical termination of pregnancy(sorry for the mention of it, no offence or insult intended) that can add to the offence from his part.
It is appropriate that you speak to a lawyer and discuss the detailed fact s and decide another future legal action against him.
Getting rejected and cheated for another woman is a pain which often leave great grief in a woman , but please know that you need to fight it and do need to be strong enough to act gracefully
First make up your mind to disconnect with him, then act against him.
Finally any time one partner can step back in a relationship, then the assessment of loss is on each one how they take it. In your case he had been cheating on you so he not only broke the promise of marriage but had intention to cheat you. Hence an FIR against him under the provisions of IPC depending on the exact facts of your case can be lodged.