I was on tri previfm (sp?) for 3-4 months then my dr switched me to Minastrin 24 fe because the tri previfm made me feel awful. i have been on Minastrin for 2 weeks and 4 days. I had unprotected sex with my bf my 10th day on Minastrin. I read the packet that came with the pills and it said I am safe to have sex after i am on for 7 days... before we had sex. But I did my own research on the pill (after we did it) and read that this pill is only 97% effective... that's not as high as my other BC... should i be worried about this?