15dpo and BFP is so faint...

So I found out on Thursday I was pregnant and AF was due yesterday so I took a digital yesterday morning and it said pregnant...so I took a test this morning with fmu and it's not much darker than thur...I thought for sure it would be a darker line than this...now I'm worried this pregnancy won't last...  :(
Anyone have the same experience with faint lines but still have a normal pregnancy??