I tear whenever I have sex

A

I finally saw my boyfriend after a month of being away and we had sex today. He always does foreplay and doesn’t just jam it in so I’m confused as into why I’m torn from the lower part of my vagina. I have a straight line going down to my anus it’s about a cm long. I don’t know if it’s because I haven’t had sex in a while or ??? This only happened when I lost my virginity for the first time but since then it hasn’t happened so I’m confused please help !!!