What Causes Spotting With Periods Later, Nausea And Pain In Ovaries?

i had sex and I spotted for 4 days and on the fithe day i started my period witch was only heavy for one day and the other two days they were light i then continued to spot and im still spotting but the blood is light read or pink. im on my 5th day spotting. I have back pain and i have a little nausea and some times i get cramps or pain on overies. Is this something to panic about? Oh im also 39 years old