Abnormal breathing?

I'm 7 weeks and occasionally I'll feel a little short of breathe or like my heart is skipping a beat. It doesn't last long or happen every day but when it does I feel very anxious which I'm sure isn't helping. I try to make myself sit down and take deep slow breathes and it's usually gone in a few minutes. Just curious if anyone has experienced this. If you have just tell me to talk to my doctor but please don't tell me anything scary that's will make it worse.. I have an ultrasound Wednesday and will be asking my doctor about it.