Very faint lines

So we have been ttc for about 6 months. I had a beta hcg done on Thursday which was 12dpo after vfl positive test at home and the results were 15.5. The doctor told me it's a borderline positive but cant confirm until Monday when we retest my hcg. I feel pregnant and I don't feel AF coming but I'm still getting vfl positives. Is this normal or should I be seeing a stronger line by now. I know I shouldn't be stressing about it but I want to be excited I also dont want to be let down again.