Spotting after sex. (help!)

So me and my DH had sex twice since we find out where pregnant.  We had sex at 7 weeks and I had some sporting for two days afterwards. I'm now 12 weeks and we had sex this past weekend and I'm spotting brown again... is common to  spot both times after sex? We're just a little leary of spotting and loosing a baby, because we had a MC in May.