Birth Control Injections & Unprotected Sex: Potential Pregnancy?

Question
i have been on the nur-isterate birth control injection since february 2009. ever since i started using this injection my periods stoped completely and i never missed my shots i always took them on time preferably the day before my actual date. i last had my shot on 16 march 2010. me and my boyfriend we always use condoms when having sex but on 5 and 6 april we had unprotected sex and he came on me. so could i be pregnant from this incidence even though i am on the birth control and is it possible to be pregnant even though you were on time for your shots? ever since i had unprotected sex my nipples were itchy for about a week or two so could this be symptoms of pregnancy or was it caused by the injection? how effective is this method of birthcontrol? is it reliable, can i trust it? please help i am scared of being pregnant so thats why i took the nur-isterate injection and they say its the same as the depo provera just that the other is given every 8weeks and the other every 12weeks. please help me am very worried and thank you for taking time to read this.

Answer
I found this link
http://contraception.about.com/od/prescriptionoptions/g/Noristerat.htm

I'm not familiar with this. We don't have it in the U.S. I did read on the link that it is a short-term type of birth control and I read somewhere else that you shouldn't use it over 2 years.

You can get pregnant using this type of birth control method or any method. No method of birth control is 100% safe in preventing pregnancy. In my opinion, putting theses hormones into your body is not healthy. I would advise you to try to find some other kind of non-hormonal birth control method.

Please email me at CHERYL51@aol.com so we can talk more. Hope to hear from you soon.

Diane Cheryl