I totally hear you, I was like this when i was pregnant with my son, I blamed it on having such a big age gap between pregnancies (18 Years, Yes 18 years lol)
When i went for my 12 week scan i said to my partner "what if they cant find anything" "What if this" "What if that"
Basically that set the president for my entire pregnancy, I worried about something then i got over that thing & then i started to worry about something else,
I wasn't like that in my 1st pregnancy & i wish that i had relaxed & enjoyed my second more.
Now that i`am pregnant with my third i`am going to learn from the mistakes i made by relaxing & enjoying being pregnant especially as this will be our last baby X