You've gotten 7 signups in a month by doing nothing but a couple posts on a few sites. There is nothing wrong with that, because you haven't done any marketing yet. Posting !== Marketing. You need to figure out who your audience is, what their pains are, how they talk about them, and get your name out where they are a looking while using their language to describe their own problems.

The list you posted of what actions you took is not that - it is you sharing a couple posts on sites that are not great for conversions. HN and reddit are good for driving traffic, but that is not the same thing. I have no idea if your product has a market or not, but you'll only find that answer if you start actually looking for the market.