So incredibly anxious... Over what, I'm not sure?

This is my third pregnancy (1 miscarriage before our beautiful, healthy daughter). I'm not really sure the point of this post, maybe to vent, as I feel I don't want to keep burdening my husband and no one other than some colleagues know yet. For some reason, I'm so much more anxious this time round. I have my dating scan on Friday and I'm terrified, I almost want to cancel it. I've no reason to be this worried. I've had no bleeding/spotting. My boobs have been sore, I've had nausea and fatigue. I feel sick with anxiety to the pit of my stomach about whether everything will be ok. I can't focus on anything other than worrying. Is this normal? Any advice to alleviate it a little? Tia xx