if I have a full time job and it's my only job I can't get a tax redound? Am I not eligible?

You still might be able to get a tax refund, it depends whether your weekly/monthly income changes day to day, if it doesn't then it probably is correct

nearly everyone is slightly overtaxed because most people don't have to file a tax return. because of this most don't bother so they lose their right to claim after 5 years.