Dealing with anxiety

Anzel • Pregnant with rainbow baby. 🌈. Due November 2019.
I am 7 weeks + 1 day pregnant with my first and I am so tense and anxious. I've had numerous positive HPT's and three steadily doubling BHCG tests. I am due for my first ultrasound on Monday. 
I am anxious about the ultrasound as I don't know what to expect and if there will be a heartbeat. I have this irrational fear that when I get there, the doc will say it's all in my head and that there is no pregnancy or I lost the baby. This freaks me out. I will be 8 weeks pregnant when I go for this ultrasound. 
Apart from anxiety related to my pregnancy, I also teach at a College, which is very demanding, and I am in the process of writing a few textbooks for major publishers. I constantly catch myself holding my breath or fisting my hands. My shoulders and back are stiff and sore. And this makes me moody and iritable. 
How should or could I deal with this? I know stress and anxiety is not good for me or the baby. Really need help.