Low betas

Sa
Hi ladies!  I am currently 4w2d after my third Femara <a href="https://glowing.com/glow-fertility-program">IUI</a> cycle.  My first beta at 4w was 49 and my second beta today was 80.  I was hoping for a number of at least 100 so I'm not very reassured.  Doubling rate is 68 hours.  Has anyone had similar betas and gone on to have a successful pregnancy?