Step moms? Teenage parents? Advice?

So my boyfriend and I have been together 2.5 years. We've talked about getting engaged soon. He has 2 teenage children. His daughter I get along with pretty well. But his son (15) is so selfish and mean.. he makes me cry on a weekly basis because of how mean he will be. He's calls me lazy and he makes fun of my appearance. I love my boyfriend and I really do want to spend the rest of my life with him; but this little monster makes me second guess myself. Idk what to do. I want to make it work, but I'm so tired of crying and of being upset and feeling bad about myself because of this kid. Does anybody have advice?

I've quit playfully teasing him, quit asking him to do anything, and quit trying to take a parental role, because I just want him to lay off of me. However, it hasn't changed anything.