You are already in a committed relationship with a child, and that is more important than a wedding ring. Why only approach this in terms of a marriage proposal?
Discuss your problems properly, and tell him his excuses aren't enough. a "bad mood" and "not going out" is a bit vague though.
My partner hates "going out" as in nights out drinking, dancing, music, even though that's how we met and what we used to do as friends for years, he's "grown out of it" (he's only 27 lol) (I'm 7 months pregnant now so irrelevant anyway). But loves to go out as a couple, meals, cinema, museum, socialising with other couples...etc which is much better anyway in my opinion. Or we have nice nights in together, meals in, films, music, board games (haha yes board games!) anything that is social time as a couple and not just sitting around sighing.
Maybe you need to approach what you both see has having a good time, especially if he's stressed with work, and the only social activities suggested are things he doesn't enjoy?