"I didn't make any off page seo to my site."
I think one of your problems maybe just that, whilst optimizing your site and make it utterly awesome is great there is no point if no one really knows about it. Part of SEO is also telling people how great your site is aka off site SEO. Try talking to some people in your niche see if there is an opportunities look into any bloggers who may find the forum a great community and want to write about it etc.