It is so hard not to worry about it isn't it.
I had the same sort of bleeding with my first pregnancy at around the same time and it started at work. I was so upset, I called my doctor and she told me to go straight home and rest till the bleeding stopped. It continued off and on for 2 days and stopped. I carried to full term no worries.
I was told by the doctor that bleeding around that time is common as it is when your body may have normally had a period if you weren't pregnant. It is very common to bleed like that particularly with a first pregnancy as your body is getting used to all the change in hormones.
If you are really concerned my advice would be to see your doctor. I did and he took blood to test my hcg levels and there were no problems. If you have strong pain or cramping with the bleeding it is best to see your doctor as soon as you can.
Hope this helps - I hope all is ok.
4 lovely munchkins DD 10/03, DD 03/05, DS 10/06 &