Dogs don't have periods, they have heat cycles. There is blood involved but the whole thing is different. It is time to keep your dog away from all male dogs until you can have her spayed. It would have been better for her health and longevity if you'd had her spayed before her first heat cycle but you can still have it done.
Sounds like your dog is in HEAT or SEASON. Something like a period. Dogs usually go into heat every six months, some can go as often and every 4 months. Have her spayed, this will happen at least twice a year for 21 days each time. KEEP HER AWAY FROM ALL MALE DOGS BIG OR SMALL.
If she is a non-spayed female, yes she will have periods, three per year I believe. You can get little diapers for her so she does not stain your furniture or carpeting during this time.
If she is a spayed female, I think she should see a vet, it could be a sign of internal bleeding which can be life threatening.