I think I can dub this “Pity Sex with consequences.”
I don’t think Lily and James truly loved each other. I think they only got married because Lily was pregnant. James viewed her as a trophy and I really wish she and Severus could have been together.
I think Lily had too much pride to be married out of wedlock. If James had really thought she was a trophy, he probably would have saved himself alone on October 31st.