Implantation bleeding and Oral Sex

Hello! I'm still a virgin. I'm 15 years old too. On March 23, my boyfriend and I had done oral sex. But when we did it, we both had our clothes on. When I was giving him oral sex, I had my underwear and pants on but i was topless. He then ejaculated on my body. I then washed it off with water and then washed my hands. And I'm pretty sure we kissed after wards. Then it was my turn. I had it clear to him to not touch anywhere around my vagina with his hands. After about 10+ mins of this, I opened and stretched the " upper lips" of my vagina BUT I DIDN'T TOUCH MY ACTUAL VAGINA! Just the skin/"lips" around it. Now when I got home, I looked on my period calendar app and found out I was fertile at that time. Of course I start worrying but not as much cause I'm pretty sure there was no contact. On March 25, I started cramping. But I assumed it was because of ovulation since the calendar said I was going to ovulate on the 24th. A week later, March 29, I started my to bleed. It was at first somewhat light but the second day it was heavy. I've been bleeding since. It's bright red, like my usual. I've had cramping, backaches, and oily skin, again, like my usual. The only thing that's different is that it started 8 days early. And it isn't exactly like my other periods. Also, the week after the oral sex, I was somewhat stressed with school and homework. 

Could I be pregnant from oral sex in the situation I'm in? 

Does saliva kill sperm? (If I had sperm in my mouth and I kissed my boyfriend, would the sperm have died before he gave me oral?

Is this implantation bleeding or an early period?

If I should test for being pregnant, when should I test? 

Please help me. This is the second time worrying and I hate it. Since I hate it so much, I'm actually going to buy myself a purity ring and don't have any sexual contact with anyone until I'm married. I'm actually pretty serious about this. So please help me! Any advice and information will help ease my stress and worry. Thank you!