Boyfriend won't get a divorce

So I've been going out with my SO for a while and I am now pregnant (16weeks). I knew he was still married to a woman that he no longer lives with and they are separated. However every time I bring up the divorce situation he try's to make excuses as to why he hasn't filed yet or even talked to her about the papers that she supposedly sent in the mail. I just need some help on what to do. I'm also scared that she won't send the papers / sign them out of spite of me being pregnant.