what should i do my employer is taking advantage of me?

[G K]

Use your spare time to learn about other companies where you might be interested in working. target your cover letter and resume to each specific company to highlight what you like about them and how your skills and experience will be an asset to them.
Get another part time job or volunteer somewhere so you won't be tempted to use your time to help thee company for nothing. (Maybe they will realize that you're serious about getting more hours if you have to be sure you're on time for your other job.)
No more freebies.
Work for yourself.