Ay, ganyan talaga ang nangyari sa akin din when I switched from Althea to Diane! A few of us sa mommy group namin experienced delayed period pa for like 1-2 weeks after the switch kasi bother ng body ang different hormone levels, lalo na if consistent ka talaga sa pag-take. Since tama naman ang intake mo at walang missed pills, siguro lang yan adjustment period ng system mo, but honestly, best na mag-check with your OB lang to be safe, especially kung next month walang darating pa, para ma-rule out anything else at ma-assure ka na okay lang lahat.