You just have to make sure your thyroid numbers are correct. Sometimes takes a while to get there. I've never had trouble with Levoth'y and have been on it for 30years. Just have to have it tested every year or until balanced.
It takes 4-6 weeks for the levo to reach full potential in your blood.
How many parathyroids did you have removed? Typically, we have 4 of them and unless all 4 are malfunctioning, they aren't usually all removed at once.
Thyroid isn't, typically, removed just because of nodules.
Calcium supplements should not be taken at the same time as thyroid replacement med. They should be separated by 3-4 hours as the calcium can inhibit absorption of thyroid med.
It's not unusual for patients to feel somewhat worse after beginning a thyroid replacement, but once your levels stabilize, you shouldn't have any trouble with it. There are those who don't do well on thyroid med, which is where the horror stories come from, but those are not the norm and most of those have doctors who refuse to do adequate testing or won't prescribe adequate doses of medication.
Whenever you get your thyroid levels tested, be sure that Free T3 and Free T4 (not the same at T3 and T4 or Total T3 and Total T4) are ordered, along with TSH. Many doctors try to treat, based on TSH only and those are the doctors that produce the horror stories you've read, because they tend to keep their patients ill, by constantly adjusting med to the TSH. Trying to treat by TSH only, is like shooting at a moving target, because TSH is volatile and can change by as much as 75% over the course of a day.
Brain fog is a symptom of being hypo, so once your levels have reached the point that's right for you, it should go away.
What dose were you started on? Typically, it's best to start at a lower dose and work up than to start right off on a high dose.