Periods can cause a dip in supply certainly. Mine came back when the Tank was 13 weeks (and still feeding at least 2hourly) and I always have a dip when I come on but it soon picks back up again.
I know you're feeling rotten. You spend weeks and weeks acquiescing to his every grizzle, you worry he's unhappy as he's a bit of a grizzler but you plod on, hoping it's going well and then something like this happens and it's a kick in the teeth. All that and trying your damndest, then you go away and he's all smiles and sleep.
Well, I don't think he's starving. He's like his big sister, he's a big baby and thriving. You know M is the same, stayed on the 99th or above for her life so far, despite being born on the 50th. Physically, it's obvious they're thriving.
He's probably quite a clever little chappie. He likes you inordinately. He likes the closeness, the cuddles, the comfort, the familiarity, the full tummy, the sound of your voice, your heartbeat. If that's what he likes best, then surely he'll settle for nothing less, why would you? And he knows you're there. He can see, smell, hear, sense you. When you nip away for a weekend he knows that you've left the building. I think he knew that that was the status quo for the weekend and there was nothing to ask for.
I know you've had a rough ride, sleep and feeding wise and you've done so marvellously. Just look at him, all 17tonnes of him. He's a gorgeous, thriving boy and you did that.
I can't tell you if you should mix feed. Certainly, I don't think he needs it but perhaps you might? I could never presume to tell you but I can tell you you're pretty wonderful.