Chances of being pregnant?

I had sex on the day after my period ended, my fertile window starts in two days. When I had sex Glow said that I had a 3% chance of pregnancy (I know people say that it isn’t always reliable as it is just an app, but I do find that when it predicts me ovulating I can see signs.) We used a condom and he pulled out & didn’t finish, I just wanted to know the chances of pregnancy for my own peace of mind.

Also, do you think condoms alone would be reliable enough? I can’t go on birth control for personal reasons (I am under 18 and my mom gave me a lecture about birth control not being good for me because I could gain weight, she doesn’t know that I am sexual active - because of what she said Im afraid to tell her) I want to continue having sex but I’m worried about pregnancy.

Thank you!