Could I be pregnant?

Hi all who read this! I'm a little worried about the possibility of me being preggo. And I'm not really sure if I could be. But, I would really appreciate the help.

On June 26, I had sex with my boyfriend and he accidentally ejaculated inside of me thinking it was another hole (I know, I don't really like the thought of doing anal, and I don't really like it cause it hurts most times). But unfortunately, it was the wrong one.

On the 28 of June, I got my period. Or so I think. I'm not really sure. Some women have said that they bleed like it's their period when they're pregnant.

I have been taking my birth control pill for a year now, and it is TriNessa.

Recently, I've been feeling nauseous, have been sleeping a good amount more than usual, urinating more than usual, and have been very irritable. At the time I'm posting this, I have been feeling sick to my stomach.

Please help. My mom would kill me if I am pregnant and my dad would kick me out of the house. I'm 17. And the thought of being pregnant scares the hell out of me. I cried before I wrote this post.

Should I purchase a pregnancy test?