Calling it quits?

Hey all, sorry if this is a bit long. I'm a grad student who recently lost about 6-7 lbs. I am 5'9 and used to be around 150 but have lost some weight and now am around 143-144 lbs. My goal weight is 138, but for some reason my body is really not liking this idea. The first 6 lbs came off pretty easily and I didn't feel hungry or uncomfortable while losing. Now, I am hungry CONSTANTLY. I try to eat foods high in protein to stay full but it seems like even after I've just eaten I have a spoon in the peanut butter jar and I can't stop. It's just really bizarre because my habits haven't changed much since I lost the first 6lbs. I have gained a lot of lean body mass due to strength training. My question is: should I stop pushing towards 138 and just eat at maintenance now? My BMI is around 21, and I feel fit and healthy. Just not sure if my body "likes" being pushed to a lower weight, my hunger levels are crazy high.