Even things like posture seem to affect my parameters. My temp will be 98.4 while seated but if I stand up and check it, it drops down to 97.9.
Body temperature measurements from outside the body are impacted by changes in blood flow, which will happen when you stand up.
Your core body temperature isn't fluctuating, the temperature at the measurement point is changing slightly because you've changed your blood flow.
We're constantly losing heat from our bodies to the environment. You could probably get similar measurements if you heavily insulated the entire area around the thermometer and let measurements stabilized.
In other words: Don't read too much into this experiment.
How do I know? Because I got so annoyed at the IR thermometers that I recently got myself one of those USB-C thermal cameras (UTi721M, specifically). It's like a 256x192 array of IR thermometers, measuring continuously, so you actually see what's going on. Lots of interesting things you can learn that way, for example that cheeks, chin and nose can easily be 1-2℃ cooler than the forehead, or that the neck/throat shows about the same temperature that the forehead, but seems more stable. And, it's much faster to take temp of everyone at home in one go. And then you also can learn a lot about your own environment, too. I highly recommend this to anyone.
That said, I found in-ear IR most reliable, and use it as a baseline for health checkups. You do however need to watch out for insertion - if you put the head in the ear too fast and measure immediately, you can get a result that's a degree or two centigrade above correct, which I imagine is because of momentary friction heating.