J.H.
L.,
First, congratulate yourself on the weight loss you have already achieved! If this is something you truly wanted for you, you have an outstanding chance of maintaining it!
Now, without knowing what type of exercise you are currently doing, how long you have been doing it and what your goals are...It sounds like you are probably ready to add some weights in. First and foremost, form is everything! You need to either look into a good trainer to show you some basic activities or if you are a good visual learner, look into a good book or fitness guide (I recommend and all of my clients receive "Training Fan--Fitness Training Guide" by Benefit Health. It's a great resource that tells you what muscles you are working, the benefits, and how to do it; even offers alternatives.) You are correct, you need a "rest" day for your muscles to effectively rebuild.
Another potential plateau point for you could be the need for interval training to be incorporated into your fitness routine. (Not all interval training involves running!) And diet is also a factor to be considered.
I wish you the best and you are welcome to message me personally either about weight training (even the Training Fan if you are interested, I am fairly certain you can buy it from Amazon, I get mine through my association.) or if there is any other question I may be able to help you with.
In good health,
J.