NO JUDGEMENT PLEASE

My period is 5 days late. I’ve been using <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> for a long time so my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period app</a> is always ON POINT right down to the day that I’m supposed to get my period. I’ve been seeing this guy that’s in a loveless relationship since January of this year. He also happens to be my ex’s brother. We fell in love. We click. I told him my period is late and he had a really poor reaction. He freaked out and was treating me like it was my fault? He even accused me of not taking the Plan B I bought and when I told him that it upset me he said it was a joke. I’ve felt loved and nurtured and cared for by this man for the last 7 months so this was out of character. I told him that he’s making me feel small and alone and scared and he calmed me down and apologized but I’m terrified that if I really am pregnant that he’s going to lose it and idk what he’ll do. Keep in mind I’m not ready to have a baby and I’ve never wanted children to begin with. I told him that if I’m pregnant I’m keeping the baby and that’s the end of it. We’re only 21. I’m terrified. What if he leaves me? What if I have to explain to my family and friends that I’m having my ex’s brother’s baby? Honestly fuck you if you’re going to say “karmas a bitch” or anything non-constructive. The way he’s reacting makes me want to take the hypothetical baby and move away. I love him so much the rejection might just shatter me completely and I don’t think I could deal with it in a healthy way. In a couple days when I take the test, if it’s positive, how the fuck do I tell him and what are my next steps? What do I do?