16dpo

my iud came out on 8/12 the period cup had an appointment to reinsert 9/13. by 9/10 I had a faint positive on a cheapie, the lines in my cheapie are coming in so slow. on 9/11 I got a positive on a frer. I went to the doctor on 9/14 and my levels are at 292 nothing to see on the transvaginal ultrasound. I feel like that's really low however they're saying it's probably just too early to see anything. I had to scans to rule out an ectopic due to a cyst on my left ovary. I hope my levels double on my second draw on 9/17. what level should your hcg be at in orderto see a sac. It says I O'd on the 8/29. wondering if i should be concerned.