Spotting still at 6 weeks...

Still spotting for the better part of 2 weeks now. Have any of you had this? I am 6 weeks along according to nurture. My only symptoms are heartburn and sore nipples. My husband and I had sex the other day and I have heard that can cause some spotting? It has been brownish with a tiny bit of pink never red. We have had 4 positive tests so far but have two more at home that I am planning on taking. Never have had a miscarriage but have so many friends that have so it is a constant worry. Please no miscarriage stories I already worry so much about that! 😞