Terrified

Hi everyone. I have been TTC for a short time since we miscarried for the first time in February. This week I have felt strange and a bit nauseous, but the idea of pregnancy didn't even cross my mind since we have not  been successful the past few months and because I had what I thought was a period last week. Today I took a test and had a clear as day positive!!  Any thoughts on this? We want this baby more than anything in the world and the idea that we could have another mc or that this was a false positive is freaking me out. Why would I have bled last week if I was pregnant? My last cycle began June 28 so that would put me at 5 weeks today. My last mc was at 8 weeks and was basically just a lot of bleeding. Any help or advice is greatly appreciated. I'm terrified.