Help/advice please.

I got back on a low carb track on Jan 18th, and 6 weeks later I'd lost a stone. Brilliant!
However, since then, I not only haven't lost any weight, I've now started putting it on! 3lb in the last week. I absolutely promise I'm having the same meals/food as I've been having since I started, and not slipped once.
I walk about 6k 2-3 times a week, that's been consistent too.
My glucose levels are about the same - averaging 6.5. What can I do??

I understand that, and normally I don't tend to weigh very often. But I'm now looking at 5 weeks of at best, being static and at worst, gaining. It's very disheartening.