precum can have traces of sperm in it

I had sex with my boyfriend around the 20-24th, and we didn't use a condom. He ejaculated outside of me, and I watched him, just to be sure. This is the first time that he ejaculated after he and I had sex. Me being afraid of being pregnant has happened before, when he and I had sex for the first time. I know that precum can have traces of sperm in it, as well.

I started to feel the symptoms but that was only because I was worried about being pregnant. I'm supposed to have my period/was supposed to have my period last week, this week, or next week. I've skipped my period before because I thought I was pregnant, so I'm wondering if it's just my brain or I'm really pregnant.

My nipples aren't darkened,

my breasts aren't tender,

I haven't been waking up with morning sickness,

I've been having weird food cravings, but I always have weird food cravings, regardless if I'm on my period or not.

I've only been really tired lately because I have work and band camp, and I've been working for about 3 and a half hours straight and been at band camp for about 9 hours total every day.

I've only been drinking a lot of water because of band camp, and because I have sun burn/sun poisoning.

My belly isn't really hard or anything.

Could someone please help me? I'm really scared....

Thanks. :)