Thanks for writing in this forum. Normally the oral contraceptives(Alesse)are taken for 21 days(active pills) and then 7 days pill free period. But if you want to take the pills continuously so as to skip your periods, then you should continue taking it. You may choose to take the pill for six weeks in a row or for 9 or more weeks. The day you stop taking the pills, you will get bleeding in three days. This bleeding is infact hormone withdrawl bleeding.
There are some side effects of taking the oral contraceptives continuously, the most important being breakthrough bleeding(bleeding or spotting between periods).The other side effects are breast tenderness, nausea, headache, mood changes, leg cramps, acne, bloating, weight changes and dark spots on the face. So if you have such side effects, then please stop taking the birth control pills and consult your gynecologist.
I hope it helps. Take care and please do keep me posted if you have any additional doubts. Kind regards.