I got my period but I think I might be pregnant help ):

Okay so I had sex with my boyfriend for the first time on October 1st and I was scared because my period was a week late but I got it and I've had my period twice since then but lately I have this feeling that I might be pregnant I feel like I'm gaining weight and I'm scared. I felt nauseous for the first time and I had a tiny dot of blood on my underwear today. Is it even possible for me to be pregnant ? My period isn't due until next month on the 7th