Didmetformin delay your period?

I started Metformin 5 and a bit weeks ago and I'm pretty sure my period was meant to start Thursday just gone but it appears to be a no show. I was a bit irregular but I had a positive ovulation test and worked out my period from there, any way the question is I know it's meant to make you more regular but did it stop/delay any ones period to start with? I haven't done a pregnancy test because I don't want the disappointment of another negative test. Also I did have the very lightest of spotting a week after ovulation which lasted 4 days. Any ideas?