If you have been newly selfish in these last two months, I understand entirely. That doesn’t make it right, only understandable. You are very young and pregnant. My guess is that the coming baby has made you take a serious look at your relationship and your life. What you are calling selfishness may be your confusion about whether your boyfriend is going to be a good father, whether your relationship is good enough to make a permanent commitment to each other as well as a child, and whether you both feel ready to be a family. It may be that you are scared to confront these difficult questions directly so you are instead picking on him about going out (and away from you and your baby).
If any of this makes sense to you, I hope you will find a way calmly to address these issues directly. You are at one of the most important junctions in a person’s life. Regardless of what you and your boyfriend do with each other, you have changed yourselves, permanently, into parents. Whether he stays or goes, he’s a father now and you are a mother. Ideally, you will decide together how to manage your time, your finances, and your relationship so you can be a family.
I wish you all well.