My Ex-Girl Friend Want To Ruin Me

I once loved a girl who was on IT in a firm i was a manager, we both went along until her ex came back in full swing to whisk her away from me. I pleaded her not to leave me but she did, I went ma way, later found a girl who i felled for, I went for her marriage introduction on 1st october this year. She’s currently pregnant for me but ma ex on getting the news of my introduction has been on my neck, she calls and text at night and has vowed to destroy my marriage claiming i dumped her which is not true. Two days ago she called and embarassed my wife calling her “a husband snatcher” and treatening thunder & brimstone. I have calmed down my wife but am still confused who gave her my wife’s number. Am i being betrayed? What should i do?