Implantation bleeding?

I am 5 weeks pregnant and had four positive pregnancy tests this week with faint lines. I started bleeding today and it felt like a period. It started brownish and went to pink and is now a light red. I have pretty good cramps too. I really don't want to lose this baby. I went to the hospital and they told me my pregnancy tests came back positive but my blood work will take a couple days. Any help?