It's very inconsistent for me :/

My record static was around 3 min, and I didn't even feel it was hard.
At other times, I barely manage 2 min.
Swimming, I once was under 2 min and didn't even notice, and yet sometimes, I can't dive longer than 30 seconds or so.

No idea why it is like that- probably because I have a chronical illness which sometimes affects my sinuses and ears.
I also never did any breathholding training, warm-up, or special techniques