I'm not a medical person or an expert by any means, but I'd reckon half a biscuit is not enough.
I found the less I ate, the more nausea and vomiting I experienced - a sort of vicious cycle, really.
Again, not an expert, but the tiredness may be a symptom of your system 'running on empty' i.e. if you're not fueling your system with food, it will become tired and lethargic.
What helped for me was I took the cyclizine first thing and then ate, say, a scrambled egg and half a slice of dry toast. Managed to keep that down, then had, say, a banana a couple of hours later followed by a small bowl of soup for lunch and so on throughout the day.
It worked for me, but there's no guarantee it would work for anyone else. Still, though, it might be worth a try whilst you pursue your GP?
It's a miserable existence being, literally, sick and tired all the time, so I really hope you find the solution on this thread and/or through your GP.