@LWood88 , there's medical evidence indicating that, generally speaking, when bg falls below 4, the body's autonomic responses (the network of systems which automatically tweak various things to keep us living) kick into action to raise bg to above 4, mainly by releasing adrenalin to tell the liver to release stored glucose.
The sweating/tremors isn't really anything to do with the low bg, it's a side effect of the adrenalin rush, just like you see some people shaking after a fright or car accident.
That's why below 4 is generally regarded as hypo.
One thing to be aware of is that over time, if you hypo a lot, the autonomic response can become blunted, so you might not be aware of being hypo until much lower levels, 2 or 3. The danger with that is that once you start getting down to very low levels around the sub-2 mark, the brain, which relies on glucose to work properly, just stops working and, as
@catapillar once memorably put it, "normal, normal, unconscious".
Not saying that to scare you, just a side note of something to be aware of. It's early days for you and it can take several years for that sort of hypo unawareness to develop, so it's not something which is likely to happen to you any time soon. It can often be mended by deliberately running higher at 8 or 9 for a few weeks.
There's always a temptation to over-treat a hypo because of the panic, which can lead to insanely high bg. There's only about 5g of glucose in an average person's bloodstream in total, so if levels are dropping, a surprisingly small amount of glucose will usually fix it. I've got cgm so can see things happening in more or less real time. If I see it trending down to 4, a mere 5g is often enough to nudge it back up by 1 or 2, but if it's a proper hypo with active insulin still on board 10 to 15g is a safer bet.