Bathing together

Okay so I was in the tub by myself and my boyfriend wanted to join. I really didn't want him to because I am so paranoid of pregnancy and I believe that if he ejaculates that it would get in the water and swim up my vagina. He got in and didn't cum but I'm still worried. Can sperm even do that, am I pregnant? I know I know I'm crazy but please help me stop stressing so much.