normally with 8mm size chance of rupture of the follicle is less,
so if that ruptured in 12th day, may be that is the reason for free fluid, but as your doctor told that there is no growth of follicle,
better to undergo scan on 15th day also,
if needed you can for hcg injection
for ovulation if your doctor suggests,
anyhow you plan intercourse in these days and also start taking folic acid
supplements which will help in case of fertilization.