Am I the jerk for getting upset after finding my pregnant fiance smoking?

I'm a 26 year old male. My fiance is 28 years old and she's five months pregnant.

We were watching a movie last night when I got up to use the bathroom.

I was gone for a little bit as I've been dealing with a nasty stomach bug from food poisoning.

When I came back from the bathroom, she wasn't on the couch, confused.

I went looking for her and found her outside on the porch smoking a cigarette.

I was furious.

Keep in mind, our unborn child is a planned pregnancy.

We've been trying for over a year and we were overjoyed when we learned we were expecting.

I am so excited to be a father.

In the heat of the moment, I might have been a bit harsh, but I was so shocked.

I didn't even know that she smoked.

After I found her and expressed how frustrated and confused I was,

she screamed at me that it was just a singular cigarette.

She also confessed that she'd been having a few shots a week with her girlfriends

and the doctors haven't said a word.

She made me sleep on the couch last night and she hasn't said a word to me since.

I just got home from work and she still said nothing.

Am I the jerk for getting frustrated with her about this?

She says it's not a big deal but I feel like it is.

I try talking to her sister, who's had a few kids already,

but she doesn't think it's a big deal either.

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