Boy issues

So my boyfriend of 4 years (on and off) ended it with me a week ago. I am about a month and a half pregnant (he didn't leave me because I was we found out after he broke up with me), but the new girl he has a thing with is trying to tell me to have a abortion because I'm ruining mine and his life (we're 18). How do I get this girl to stop and leave the both of us alone. Also I still love him and need any advice on getting him back :( we've never broken up this long before.. He broke up with me cause he just didn't wanna be with me?!? Help:(!