Cramps when stressed

I’m pregnant for the first time with twin boys and currently 17 weeks. I’ve noticed that when I get stressed, upset, etc. I start cramping. Is this normal or does this happen to anyone else? Once I notice it, I immediately try to calm myself down because I’m afraid something bad is going to happen but I can’t help but worry. I even had an ultrasound early this morning and everything was great but the stress cramps really scare me. Any advice?