Sex before 6 weeks ... ?!

Started having sex around 3 weeks post pardum. My bleeding lightened up an was pretty much done . Ended up going to my ob around 3 weeks because it was a follow up for a bladder infection .  he said everything was fine inside an started me on bc. Has anyone experienced getting pregnant right after delivery ?!! Used a condom one time it sucked .  So been doing the pull out method while taking the pill. Bleeding has came back but is light not enough to fill a pad . I was told by my nurse it's normal especially cause I started working out again an taking the pill. Just nervous I can't get knocked up again but ugh sex feels so good . Mind you I had a easy birth vaginal with no tearing or abrasions .