I bled my whole Pregnancy with my now toddler. I had hematomas that caused the bleeding. It's also rare to have a period whole pregnant, but it does sometimes happen. As long as you aren't having strong cramps like contractions I think you'll be fine. I spotted with my first pregnancy and by the end of the day I was having full contractions and lost the baby at about 10 weeks.
Not to freak you out, but my second Pregnancy was normal except for then periods.
Some women do if their progesterone levels are too low - it will happen at the same time as your period would be due but noticeably lighter and shorter than normal.
You don't get your period when your pregnant... are you bleeding ??