I need your advice please

Hi, I'm from the UK I have been diagnosed with pcos and been ttc for 4 years 5 months. I have 2 children, my eldest is a girl nearly 10 and a boy who is 6 and a half. I have been taking metformin for over a year now and my cycles became regular (was having 35-36 day cycles but my last one was 33 days), my period this month should have started between 9th May-12th May but I'm late by 5 days and I don't know whether I should do a pregnancy test as I hate seeing a negative. I'm supposed to starting Clomid too.🙁

PLEASE HELP!!!!!