What Causes Delayed Periods And Spotting?

I'm on Omeprazole...2 a day...my period is now 6 days late i had some spotting a couple weeks ago and period before that for 2 days, very light. i'm on micronor mini pill. i'm 27 and about 12stone, 5"2. had a gastric bypass nov 2009 lost 10stone so weight is not the issue. just want know if the omeprazole could be affecting my cycle or if i should get a pregnancy test?