If things don't start improving again in a reasonable amount of time, say a year, start working together to get back to a level that the both of you will be happy with. Get a baby sitter once in a while and rediscover each other (grandma & grandpa are good for this). You can't do anything better for your new child than to raise him/her in a home with two loving and still in love parents (and that means regular lovers).
If once a month seems like an eternity for you to wait, then it will always feel like there is something not quite right about your M anymore. This is important and a mistake I regret not addressing after our child was born.
