Help, I’m so worried.

I had unprotected sex on January 3rd.

I used to have my period on the 20th of every month. (I’m not that regular, my period is changing between months of being in the same day, that’s my regular period)

My period came earlier that month, it came on January 13th, it lasted 3 days or 4. (that’s my normal)

But then I started to worry i don’t know why.

He came and then we did it again and I think that was our mistake.

Now today I’m feeling nauseous, and I have cramps.

What do you think? help :(