While the amount of blood lost is less, bleeding may be at irregular intervals and there may be spotting between periods. Mini-pills tend to make periods very short and scanty. You may go several months with no bleeding at all. You have to remember to take a pill every single day. So check your pack each morning to be sure that you took yesterday's pill.
Some women use a backup method as long as they are on mini-pills.
Progestin-only pills do not protect you from HIV or other sexually transmitted infections. Use a condom if you or your partner may be at risk.