I had unprotected sex with my partner . He's not HIV infected and neither am I. After having sex I had an oral contraceptive and that too within 3 hours. We're worried since after 6 days from the date we had sex I started bleeding , it lasted for 2 to 3 days and then stopped , it was slightly lighter than normal bleeding . Am I pregnant ? Should I be worried... and get myself checked ?

Were the pills you took your normal birth control pills or were they emergency contraceptive pills? Regardless, pregnancy will still be a possibility as no contraceptive is 100%, even emergency contraceptives.
Odds are you aren't pregnant, but it wouldn't hurt to take a test. If it is negative, just see how your period is the next cycle. More than likely it will be fine, but obviously take precautions before having sex again.

@ Doulalc

It was an emergency contraceptive pill and I took in within 2 hours , it's 97% effective if taken within 24 hours after having unprotected sex. Since then I've been using precaution but thank you for your help , was very worried.

Well one could argue the 97 percent effective depending on the study you want to believe

But yes, you can be since it is not 100 percent effective