lost 20 pounds in 1 month is this good?

Depends on which "diet" you are following ...

on LC I lost 22 pounds the first month ... and have kept it off --- I was "bigger" so my dr wasn't shocked by the loss ...

What are your stats?

Did you just start? You may have lost a good bit of water weight in the beginning.

If you are obese and on a VLCD that is supervised by your doctor, sure it is healthy, for certain values of healthy.
Otherwise you may want to slow down to no more than 1.5% of your body weight per week while you are obese.

And if you would like to preserve the maximum amount of lean mass while losing your weight you may want to slow it down yet another notch, down to 1% while obese/overweight and 0.7% when overweight/normal weight and lower than that in the bottom half of your normal weight range.

The reason being that the less fat you have available to lose, the harder it is to only lose fat.

Normal MFP recommendations (as per me ;-), are:

Target of 0.5lbs of weight loss per week per 25lbs you are above the bottom of your normal weight range.

Minimum NET calories after accounting for true net exercise calories of 1200 for females and 1500 for males. I personally would prefer to calculate my maintenance calories at goal weight at the lightly active to active setting and, as long as the deficit was sufficient, try to lose my weight by eating somewhere around that level, minimizing the need for my eating to change when I get to maintenance (and eliminating the belief that my eating is supposed to change once I am in maintenance).

If you are using MFP estimates and have a large deficit start by eating back 70% of your exercise calories and adjust according to your actual losses after 5-8 weeks. If you have a small deficit start by eating back 50% of your exercise calories and adjust according to your actual losses after 5-8 weeks.

if no kidney problems and wanting to preserve lean mass, target of 0.8g of protein per lb of bodyweight

minimum fat consumption of 0.35 to 0.45g of fat per lb of bodyweight

25g (female) and 38g (male) minimum target for fiber a day for your personal comfort

The rest can be whatever combination of FATs and CARBs strike your fancy

Weight yourself daily and input your weight in a trendline type application such as www.weightgrapher.com (www.trendweight com with a supported scale, or a free fitbit.com account to enter your weight through), or happy scale on the iPhone. This allows you to focus on real changes as opposed to chasing your tail around trying to adjust for changes having to do with glycogen replenishment, carb re-feeding, salt consumption, changes in exercise, hormones, or TOM issues-which I sincerely hope will not be impacting you as a male!

Get a fitbit or jawbone or misfit, or use a phone apps such as Pacer to count your steps and slowly increase your activity level and or exercise (you don't have to start exercising like a gerbil in a wheel in order to lose weight; but a little bit of extra activity and later on some muscle preserving exercises may not be a bad idea)

To maximize lean mass preservation lift progressive weights (or start with bodyweight exercises) when your conditioning allows you to do so.

A lot of it was probably water weight. People who go for an extreme deficit at the start of their journey can easily lose ~10+ lbs in the first week.