The only unpleasant side effect I know with progesterone is that it helps sensitize estrogen cells, and can make your estrogen symptoms feel worse at first. Then that calms down, just as with the iodine, and you feel the calming that progesterone provides.
If you use too much, you'll feel sleepy. That'd be a clue not to use so much. You can use a bit morning and night rubbed into your fatty tissue.
Consider using some progesterone to support the second half of your cycle. But of course, be comfortable with whatever decision you make. It's all a process that we have to feel our way through. I've had to revisit my decisions numerous times over the years, always grateful for another chance to get it right.