18 Weeks. Worried😢

This morning I got very dizzy and lightheaded and ended up blacking out for a couple seconds. I felt fine after a minute or two of waking up. But I wasn't sure if my baby girl would have been effected by it. I didn't fall. I was sitting next to my husband, and he caught me. I grabbed a stethoscope hours later just to see if I could hear her heartbeat, but I can't😢 the stethoscope is nothing expensive. But I wasn't sure if I would be able to hear it at this stage in pregnancy (18w2d). I have my anatomy ultrasound on Monday, but I'm just still so worried. Any similar stories? I just want to know she's okay