First time mommy

i'm 7 weeks preggy, 2 weeks ago nag bedrest po ako kc may spotting akong blood. kakatapos ko po mag ultrasound kahapon, and may nakitang subchorionic hemorrhage ? hays.. ano po kaya cause nya ? as advice by my OB, i need complete bedrest for another 2 weeks. sad 😔 pano maiwasan mga momsh