Hiiiiii! I've been on a LCHF diet for three weeks now. I joined this forum because I have questions I'm hoping you all could answer
I'm 31, I'm breastfeeding (in the process of weaning my 16 month old), and I'm 16 lbs over a healthy weight (according to bmi calculators), though my goal is to lose a total of 20 lbs.

My first week, I lost 2 lbs, but I've gained back those 2 lbs since then. So, I've cut out cheese and started fasting 16/8 (I eat from 12pm-8pm).

This is an example of what I eat:
Breakfast: green tea with coconut oil
Lunch: big bowl of spring mix salad with bacon and chicken, avocado, and ranch dressing
Dinner: green beans, hamburger, and bacon

I drink seltzer water without any sweeteners throughout the day.

So, why am I not losing weight?

Hi there. Your meals seem on target. I bet the breastfeeding is having an impact, since hormones are critical. How do you feel? How do your clothes fit? Sometimes, the scale won't tell you. My bet is if you keep this up, finish weaning, and watch not only the scale, you'll start seeing changes soon enough. Plus, you don't have much to lose, so you may just find it takes a while.

The advice, just to be on the safe side, has always been to only lower carbs to a moderate level. Consider saving the fasting and VLC to when baby is completely weaned. Some good articles on what you can do in the meantime here: https://www.dietdoctor.com/?s=Breastfeeding+
Congratulations on your new family.

Is your baby getting a lot of milk still or just the comfort nip now and then?

If you are not eating enough overall to cover your metabolic needs plus making milk, I could see a kind of "hunkering down" for your metabolism.

Or maybe it's just the breastfeeding hormones.

Also, BMI is not great if you have dense bones and lots of muscle. What's your build like? Maybe you are closer to goal than you think so losing "pounds of fat" is slower.

I mean enough food to stoke your metabolism so it can burn off the stored fat. It's a sweet-spot balance - you have to eat enough for a strong metabolism but not so much that you stop fat loss.