The Plot Thickens

Or, in my case, I feel like I'm the one that's thick!
Everything seemed to be coming along just nicely with my latest work. I'm making more notes, formulating plans, mulling over ideas. So far, so good. Then I hit a kerb. Suddenly I'm flying at a wall, and I know that if I don't take evasive action soon I'm gonna crash and burn!
I understand, now, that I've been neglecting the plot. Not only that, a relationship between two people in the story, that should have been so easy to fit into it all , just seems like an impossibility, to the point that the story may have to get along without it. But I don't want this. So, in order for it to exist, I have to search inside for reasons and circumstances that previously weren't there. Or were they there, just I hadn't explored them?
Will the story actually be long enough to allow such a relationship? An answer to this may be that I really have to create more than I had originally planned. That my planning, thus far, has caused me to enter a world that I didn't realise - or at least, fully realise - was there.
I'm very happy with everything I've been doing with it all, right now. I just didn't expect something that was in my head from the very beginning - long before a lot of stuff I've been dealing with lately - to be causing me problems. I'm going to have to consider some things and not go any further with my other thoughts until I've resolved them.
Yeah, I know: no pain, no gain. Obviously, I was enjoying this a little too much!