I had this problem with A Greater World and swore it wouldn't happen with Kurinji Flowers - but it has.
I've had to resort to creating a spreadsheet (aaaagggghhhh!!!) to try to exert a bit of control. It's such a nightmare juggling act - trying to wrestle with timing pregnancies, making this work with when people get to have sex (doh!), other people popping their clogs and mixing all this in with world events (the book is set pre and post the second world war). I've been climbing the walls in frustration. Then I stupidly decide to move chunks of text around and forget where I've put them, end up repeating myself, deleting bits I didn't want to delete or ending up with things happening out of sequence.
Anyone who thinks writing a novel is easy work is seriously deluded. Add to all that trying to do it while also watching the Men's Finals - or today fielding a succession of telephone calls and it's a recipe for serious frustration/ madness.