Am I in a deficit

As long as you don't lose weight too fast, 1200 is fine (which is more likely if a shorter person).
Too fast, my opinion: Losing more than 1% of current weight per week, and for many people, 0.5% would be better. The actual loss rate on average over 4-6 weeks (whole menstrual cycles if you have those) tells the truest story.

If all your estimates are correct, eating, 200 below maintenance calories, and burning 200-300 calories every day above maintenance calories (doing something that wasn't included in the activity level you used to estimate maintenance calories) . . . it would be reasonable to expect to lose about 0.8 pounds to 1 pound per week, on average. If the exercise isn't every day, it would be slower than that.

Repeating again, because still true: The actual loss rate on average over 4-6 weeks (whole menstrual cycles if you have those) tells the truest story. It's all estimates, until the results are in . . . at which point it's only a better estimate.

Once you have that multi-week average figured out, you can adjust calorie intake if needed, using the assumption that 500 calories a day is about a pound of body fat a week (and obviously, use arithmetic to figure fractional pounds).

BTW: Hunger isn't necessarily a perfect guide to whether calorie intake is sufficient (or excessive). It's possible for people to feel hungry when gaining weight, or reasonably full when undernourished or losing weight too fast. Again, the real-world multi-week results tell the story.

Best wishes!

Are you're sure your maintenance calories are really just 1400 and not your BMI without any activity? I just tested a few things with https://www.sailrabbit.com/bmr/ and would get a TDEE (base metabolic rate plus any movement) and would get this with a 60 year old woman being 50kg (110lbs) and 150cm (59 inches) tall who has a total sedentary lifestyle and works a desk job.

I'm not trying to tell you you're wrong but still question this a bit. With exercising though your TDEE cannot be 1400 only

ryleighjader12 wrote: »

I am a short female (5’1) and every time I calculate my BMR, I get around 1400 as sedentary (I’m too paranoid to add any activity if that makes sense lol).

A few months ago, I lost around 20 lbs. Now, I eat more than I used to but burn a lot more than before so I am confused why I am hardly losing weight like I was before.

Honestly, it doesn't make sense to add zero activity to BMR to estimate maintenance. I think you're maybe not really considering the definition of BMR: Your BMR is the number of calories you'd be expected to burn flat on your back in bed in a coma. Your BMR at sedentary is the same as your BMR at very active: It's just the baseline number of calories it takes to be alive, not doing anything.

On top of BMR, there's:

1. NEAT, non-exercise activity thermogenesis, the calories we burn doing our job, home chores, grocery shopping, etc. - the average daily humdrum.
2. TEF, thermic effect of food, the calories we burn just digesting/metabolizing what we eat. Yep, BMR doesn't include that.
3. EAT, exercise activity thermogenesis, the calories we burn doing intentional exercise beyond the daily humdrum.

Your maintenance calories include BMR plus all of those things. It can be significant.

You might consider taking a look at this calculator, which makes all of that explicit:

https://www.sailrabbit.com/bmr/

That one lets you compare various research-based formulas for estimating BMR (which isn't some universally-correct thing either, just an estimate), then look at the effect of different levels of activity on top of those BMR estimates.

Most people will be close to the research formulas, but individuals can be higher or lower for no obvious reason. I'm 68, 5'5", 133 pounds, sedentary before exercise. I'm even severely hypothyroid! The BMR estimates for me - without even considering the thyroid thing - range around 1200 calories. If I ate 1200 calories, I'd lose like a house afire, dangerously fast, around 2 pounds a week, a completely idiotic plan for someone my size.

I admit I'm a mysteriously good li'l ol' calorie burner, but sincerely, lowballing all the estimates isn't a good idea. It can become a self-fulfilling prophecy, if we drag through our day because of underfueling.