It sounds like you either need to move in together or get a hotel room every weekend. It doesn’t sound like your have any issues with your sex life at all except not getting to have it often due to your circumstances. Using pheromones isn’t going to make your girlfriend f*ck you when her parents are home if she’s not doing it now.
I think you should read this: What pheromones can and can't do: realistic expectations for newcomers