can you have symptoms way before your period?

A
Hey guys!
We weren't really TTC yet, we were planning on starting next month, but we had sex without any protection a a few times after my period.
My last period started the 3rd and today is cycle day 15 but since yesterday I've been getting cramps (not too bad) like I'm about to get my period and that's 12 days away still!
I've been nauseous and also as webMD and google say is heartburn.  I've never had that before and I'm not one to be nauseous ever.  I have an iron stomach, and I haven't eaten anything out of the ordinary.
I've also been super tired, I had to take a nap...  I have ADHD I don't ever take naps.
I didn't even think about pregnancy yet because well were not trying and I thought it took a few tries, but this is too weird.
Am I crazy?
Can you even have symptoms this early?
Has anyone had them this early?
Thank you ladies