It is posdible to get pregnant while on birth control. Any type of protection is not 100% effective
Based on what you've said, I don't think there is anything for you to worry about. You're on the pill, so even if you had sex with him, you're still protected. Any strange period issues are related to being on the pill, which can change the consistency, color, timing, and overall appearance of your period so don't worry about it.