Hi So I'm Freaking Out About Being Pregnant. This Panic

Hi so I'm freaking out about being pregnant. This panic happens every once in a while. I'm on birth control, tri-sprintec to be exact, and I have unprotected sex with a boy I'm talking to. It's been about three months and I've been fine. But recently I've just been feeling very weird. Last time we had sex was the 11th and he didn't even finish, which he never does inside me. He always pulls out. I got my period the 20th of December and I took a test today which is 3 weeks from when we had sex. I should feel relieved right? But my body still feels so weird.