Don’t mess around with your body to suit a wardrobe of clothes! Eat a healthy, nourishing diet and exercise in moderation for health and pleasure. Your weight should stabilize, and your measurements will, too, eventually - though they can shift with change in exercise routine and age. Yo-yo dieting messes with your metabolism!
From age 30-55 I weighed 150-155 lbs, but in 2016/2017 after training more rigorously than my norm for a special triathlon event, I dropped about 15lbs. After the event (September 2017) I expected the weight to creep back up, but it never did. I now fluctuate between 136-140 (5ft 7in). I weigh myself once a week on a scale that also provides fat/muscle/bone/ and water numbers which I document in my training log. I don’t get too hung up on the numbers, and strive rather for consistency/maintenance. Since my weight is within the norm for my height and build, I’m good with it.
I don’t know if it’s an age and/or hormone thing, but my friends in their 40’s and 50’s seem to struggle with their weight/size more than those in their 60’s and 70’s. Though generally thinner, my older friends have lost a lot of muscle mass as well as body fat.