My issue is that I have problem with my menstrual flow, 3 weeks ago I and my boyfriend had sex even though he pulled out I used contraceptives, then 3 days later I had sex again he pulled out but I didn't use any contraceptive, I noticed that my period came 4 days after (my cycle was 13 days instead of the normal 21 or 22 days cycle I used to have, the period lasted for 4 days) then last week sunday I had intercourse again and I used the contraceptive, I was supposed to see my period last week tuesday but I haven't seen anything till now and I have done the pregnancy strip test it came out negative 4 times. And till today I haven't seen my period. I want to know what is wrong.