What Causes Gummy Discharge During Periods?

When i get my period, my discharge is sometimes gummy, but it has been like that since I started puberty. Then when i started having sex, i noticed that every once in a while, my discharge would be a little white and gummy, but it was so infrequent that i didn't think it was a problem. Now, however, it has happened more often. I have been on the pill for almost 3 years now, and recently have had unprotected sex with my partner. Is this a normal reaction?