Threatened Miscarriage

So i went to the ER. Got a pelvic exam, blood work, and ultrasound done. I was experiencing cramping and then brown discharge and some red blood. They seen a sac, couldn hardly see the baby so they say I am in my early pregnancy. Mentioned sometimes its normal to have bleeding in early pregnancy. But to shorten everything up I cant have sex, lift anything heavy or even be too active i have to rest. Until my obgyn say otherwise this following Monday.. the only thing we can do is just wait n see if i miscarry or pregnancy be a success..