HELP!

Ive just finished month 4 of microgynon 30 & i was meant to come on my period Monday (i have come on on this day for the last 3 months & been very light) but i havent yet & showing no signs of it starting. Me & my boyfriend have had unprotected sex but he hasnt finished inside of me for about a month (i did 2 pregnancy tests the day i was due last month as something didnt feel right & it was negative). Is this lack of period normal? I dont think im pregnant but im starting to worry! Ive not missed an active pill (only missed one placebo one last month as i dropped it & lost it but my doctor told me it was ok), the past month though i havent taken it bang on time due to working but i was never 12 hours late+, only ever 6 hours max. 

Any help would be amazing! X