Do pregnancy test in case you miss period

First need to do a ultrasound.

Pain can be due to ovulation  pain  or ectopic pregnancy  so consult  your gynaecologist  personally

You need to consult a gynecologist to check. Left sided pain isn't a symptom of PMS or of early pregnancy. Need to check for an ectopic pregnancy.

You can continue Capsule Susten 200 mg twice a day for a week and if you still don’t your periods you can do a pregnancy test with morning sample fasting urine

You should do a blood test Beta HCG. It will confirm if you are pregnant

Wait for 15 days post IUI for doing urine pregnancy test. You need to judge how much the pain is. If it is unbearable, you need to consult a qualified gynaecologist at the earliest. Sometimes and more so in cases with difficulty to conceive, there are chances of ectopic pregnancy, that is pregnancy in the wrong location. So you need to be alert. Judge your pain and act accordingly.