Hi Dr Andrew I Was On Injection When I Stopped

hi Dr Andrew
i was on injection when i stopped for 8 months , recently decided to go back to prevention so started using triphasol prevention pills, am almost on my third line ( brown pill ) and haven't went on my periods
i read that after 2-3 days taking the red im suppose to go on periods but haven't till today. my question is should i be worried? what are the chances of me being pregnant?