“cautiously optimistic” first ivf advice needed

As

my fertility clinic told me those words today. i got a positive pregnancy test yesterday 8dp5dt (fresh transfer). i started light bleeding last night and today is now heavy. my beta this morning was only 17. they said it was a “low value positive” and to repeat on friday. i’m feeling so discouraged. has anybody had these same results/symptoms and gone on to have a viable pregnancy?