What Causes A Lump In Uterus,dark Periods And Sore Breasts?

Hello.So I had unprotected sex about two and half months ago.I started getting symptoms of pregnancy about a month after.I took four at home pregnancy tests.Two cam up positive two neg.I am rh negative also.My last two perios were so like only four days long and the blood was mostly brown no bad cramp?Anyways my breats are very sore and I look prego .I felt right below my belly where the she utereus is and there is a lump I think I might be pregnant.My mom bled with me through the whold pregnancy with me and her first pregnancy shenever tested positive at all she had to get a ultra sound to find out.What is your opinion on what I should do?I'm am very scared as I have had quite a few miscarriages and found out its cause I am rh negative so if I am I need to know if I need my rhogam shot im terrified.I don't want to lose another baby.