Possible physical causes of what is happening this week
Lump on neck at base of skull - possible enlarged lymph node; a sign that you’re fighting some sort of infection.
Feeling ‘odd’ for few days - could be sign of viral infection such as flu or, as a lot of people are experiencing this winter, the bug doing the rounds that is making people feel so rotten.
Feeling weak in the knee area, coming over very hot and feeling like you’re going to faint - could all be due to blood pressure dropping (again could well be due to a viral infection); or, could be due to drop in blood sugar - not a lot for lunch, followed by a chunk of Turkish delight giving a sugar rush. The pet shop may have had their heating on, if you also had outdoor clothes on you may have started overheating which can cause a fainting episode.
The feeling of some sort of blockage in you abdomen could be something as simple as constipation; you could have enlarged lymph nodes in the lining of the gut (a harmless condition called mesenteric adonitis) which are caused by fighting and infection - often viral.
Despite your concerns regarding diabetes or something blocking your abdomen, your symptoms aren’t indicative of either condition but far more likely that you’re suffering from a viral infection that’s caught you on a bad day; you probably need to increase the protein and carbs in your meals for a few days to stabilise your blood sugars or eat small amounts more frequently but, more importantly, make sure you’re drinking plenty of fluids as that will help increase blood volume and reduce the risk of blood pressure dropping and therefore reduce the risk of a near fainting episode again.