I have pcos, pregnant 7.5 weeks (based on lmp, but have irregular period). Ultrasound said fetus doesn't have heartbeat. Should I go w/ d&c or wait?

Wait, repeat sono. Wait, do not rush. Since you have irregular periods wait. Do bhcg quantitative and progesterone levels. Repeat sono in 2 weeks and correlate.
There is data. There is data that suggests if you are having a miscarriage than the best thing to do is have a d;c rather than wait if your doctor confirms the pregnancy is not viable. By 5 weeks a heartbeat is often detected. Good luck.