I`ve just conceived within the last 2-3 weeks also, and OH and I had sex after I`d gotten the positive result...and I had very slight bleeding, a few small red tinges when I wiped. A day or two later, no extra or increased bleeding, and actually an area on my vulva was a bit sensitive, so I think that is what caused the spotting.
Anyways, during my first pregnancy, I had a slight hemotoma that caused a decent amount of blood both at 10 and 34 weeks. During the first bleed, we had just had sex, and that latter, we had not. Suffice it to say that I am not comfortable with sex now, but we are intimate in other ways so it`s all good. My daughter was born healthy, no issues, but best to be cautious...