Hang in there! 4.5 pounds is still really great! I don't know if your center has this, but there's a little model of what one pound looks like and it's alot!
Trust that you are doing the best for your body. There are a lot of changes going on in there with weight loss... your fat cells, your muscle, your hormones, everything is working together and affecting good changes for you.
There were many weeks that I would only lose a pound but my clothes fit so much looser. I went from a size 20/22 to a 9/10 in pants... everyone's different.
Also, a little note on stress... I know it's difficult but try not to stress... for me it made me gain as much as 2 pounds in a weigh in!
You're doing great! Try to relax and take advantage of the help that is available to you!