Tell me there's a happy ending to this story!?

So im about 5 weeks pregnant I have taken two tests and gotten faint lines both times first pee of the day couple days apart. Well today I went in to the drs to pee and it came back negative but I told her my symptoms:

Missed period

Bad Cramping day before I was suppose to start my period lasting a couple days(zero blood)

Nausea

Increased appetite

Tender breasts, like hurt to wear a shirt last week.

She had me go get my blood tested for hcg levels.

She just called me at 7pm to tell me my hcg levels came back positive but on the low side and told me I could carry on to have a normal pregnacy but there is a chance I'm going to miscarry or I have an ectopic pregnancy. Im suppose to get my blood taken on Monday and she will call me Tuesday to discuss my results and next plan of action.

I'm freaking out. Ive had two healthy baby girls. Ive never experienced a scare like this.

Is this normal to be low at 5 weeks. Any one else have this happen and have success.

I also never needed a blood test before because I had positive urine tests from Drs office both times before, so I dont even know what my hcg levels were like for my first two.

I also drank 1 gallon of water that morning as I normally drink a ton of water so she had thought maybe I watered down the urine test but that doesn't explain the blood.