I'm a total beginner and really appreciative of any advice here. I'm making a 1 gallon batch of IPA from a kit. I brewed 16 days ago, and in the first 48 hours of the wort being in the fermenter it was bubbling away like crazy. It then settled down and I could see the liquid become less opaque and darker, as the yeast cake formed at the bottom. Today I went to look again as I had planned to bottle this evening, and it's more opaque again, and looks more active. What could be the cause for this. The last few days have been slightly warmer here (it's gone from ~20°C to 25°C), could it be the temperature variation?
In addition to this, I have been measuring the gravity with a refractometer every 3/4 days just to see how it was changing. After the first 3 days it had dropped to 1.034. Since then (almost two weeks now) it has remained at that value, so I thought fermentation must have been over? I have tested my refractometer on water and it seems to be calibrated well. Either way, poor calibration wouldn't account for the value not changing at all.
So, in summary, why does my wort suddenly seem more active again after 16 days, and why hasn't my gravity measurement changed for two weeks?
Thanks in advance for any help!