Confused by BG readings today.......

So I'm still learning about how to manage my diabetes and have learnt a huge amount from this forum e.g low carbing and have consequently got my HbA1c down to 40 from being in the 90s. I thought I pretty much had understood the basics but my blood glucose readings today have confused me......

I woke up with a reading of 7.4 at 7.30am which was good for me (always higher in the mornings than I would like, usually between 7.9 and 9.2), I took 10 units of novorapid and was down to 6.7 by 11am after having a couple of coffees with cream. I didn't have lunch as really busy at work, just continued to have another couple of coffees with cream. By 4pm my BG reading was 7.2????

I would have expected the BG reading to continue to go down rather than up given how little I had consumed - I don't think I had a hypo as I didn't experience any symptoms and so I don't think this reading was a rebound effect from a hypo - why has my BG crept up rather than gone down?

I hadn't considered stress .......

I don't think it was any more stressful than usual (more often than not I end up skipping lunch)....yesterday was FAR more stressful and I was even in tears (horrible work colleague) but my BG didn't rise - can stress have a delayed effect? Only asking as I've noticed if I have had a 'high carb' day often my BGs will be slightly higher over the course of the next day so perhaps there is delayed effect?