How to make my clothes fit better?

In the past few weeks I have been going to the gym. I lost 5 pounds and my clothes are big on me. My mom wont get me new clothes because she feels that I am going to loose more weight and it will be a waste of money. A lot of my clothes are getting big on me and I want to shrink them so they will fit. I have this pare of shorts that I want them to fit tighter and snugger. My bra is even getting big on me. Please let me know how i can make everything bitter fiting. Thanks <3