Why is ex such an *** and a waste of space?

Ex left me wen i was 5months preg.never seen him since.i gave birth 4months later n have been bringin my son up alone.i have just found out my ex is engaged n going out with a woman with 2 kids yet he had asked me to get rid of my baby as he didnt think we could afford it but he can afford t support someone elses kids n pay for a wedding.they got engaged 6months after he walked away.i dont get a penny off him to support my child as all of a sudden he cant hold down a job.he has another kid with someone else that he doesnt bother wih either.why is he more interested in kids that aint his