For me, week 3 was the worst. Then I turned a corner. Keep at it, it will get better.

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It's a replacement hormone for what you're not making enough of. You can have symptoms from over or under-replacement, but those are common to all of us when we're not at the right level. You MIGHT have side effects to one or more of the fillers in the pills, but not to the levothyroxine itself. Your body can't tell the difference between natural and synthetic T4 hormone. Ignore most of the scary stories on the Internet. Out of billions of people, there's always a few with issues.  There's 23 million people in the US alone on hormone replacement due to hypothyroidism, and the majority of us are doing fine. More on reddit.com

I started at 25mcg and it made me feel incredible... because i had felt like absolute shit for so long. More on reddit.com

It’s possible the dose is correct ultimately but you may have started too high. For me, 50 was too much and then after dropping down to 25 even that felt like too much for a week or so. However, after letting things settle, I feel hypo again and will need to raise my dose (confirmed by lab work). I’ve read some similar experiences on here before where you need to ease into it by starting at a lower dose initially and test at the end of 6 weeks to see if an adjustment needs to be made. Let you dr know what’s happening and see what they say. More on reddit.com