Had protected sex a month ago bt period is unusual with less & dark couloured blood.could i be pregnant?

Safe protection: The pill used properly is the most reliable protection. Iud is the next best protection. The use of spermicide foams is very poor protection. The condom has up to a 35 percent failure rate depending on its integrity. In your case where this is an unusual period for you it would be best to check with an over-the-counter pregnancy test to be certain of your situation.