Do you get cramps, if you have an unviable pregnancy?

I've recently found out that I am pregnant, should be around 5 weeks and 5 days now, not 100% sure due to irregular periods prior to conception, actually I hadn't had a period for 3 months prior. I've been having mild cramping which I was concerned about but reading online it seems fairly normal. I've had a few days of slight queasy feeling in my stomach but no major sickness. I also have swollen and sensitive . I am concerned that due to irregular periods before that maybe this is an unviable pregnancy and was wondering if you still get pregnancy sypmtoms if this is the case. The dr has told me not too worry too much and just get an ultrasound in about 2 weeks.