Round Stomach, Discharge Of White Jelly Substance After Periods, Nausea. Possibility Of Pregnancy?

Hi. I just turned 13 and if A female doctor can help me that would be appreciated. :) I turned 13 in march and me and my boyfriend have been sexually active since June 29. Our parents are aware of us dating but not being sexually active. We always use protection and the last time we had sex was on July 13. My period came early on the 17 of July and my periods usually comes on the 23-24. It didn t surprise me much because I have a thyroid problem and sometimes my hormones are just out of Wack. Then about two days after my period had ended I was looking at my stomach and it looked a little round. I wasn t sure if I m pregant or just gaining weight. The next day I looked in my underwear and I noticed some type of white jelly type thing which had no smell. I got a little scared and looked up pregnancy signs and I didn t really have any except for being nauseas. But its only for about two minutes and it rarely happens. The website said that sometimes when your body is getting ready to have a baby you might have light blood with some cramping that may be mistaken for your period. But my period lasted 5 days like normal. I can t tell my parents about this or anyone older than me so I really need some help or advice. Thanks!