Implantation or ovulation discharge?

Hey, I'm Shaelee. I'm 19 years old. I had my period from the 4th to the 8th. Then, on the 11th, I had unprotected intimacy with no pull-out. My period tracker suggests my ovulation was from the 9th to the 15th, but my cycles are irregular, usually between 20 to 28 days. On the 15th, I noticed a specific discharge once, and today's the 16th. I'm having period-like cramps, tender boobs, and feeling nauseous. What do you think it is? I need advice.