I had my tubes tied last March, but then started having periods every 2 weeks. So, doc put me on Lo Loesterin FE to regulate. For the last 9 months, my periods have started on day 4 of the placebo pills. But suddenly, this month, no period. I took 4 pregnancy tests over 4 days and all were negative. My husband and I also use a spermacide (can you tell we don't want kids?) But I'm still worried about not having a period. It's my only assurance of not being pregnant. Should I be worried?