I had thin lining - there are usually one of two issues: sleepy oestrogen receptors or poor blood flow
Do you get EWCM?
Have you ever used the clearblue dual hormone OPKS? If so do you get high readings (showing rising oestrogen levels)?
When you've had ultrasound have they ever used the doppler to look at your uterine artery blood flow?
For my my chronically thin lining was due to non responsive oestrogen receptors - I simple wasn't making enough oestrogen. So I didn't get any EWCM, my OPKs never detected rising levels of oestrogen - they went straight from low to peak
My uterine blood flow was spectacular. So all the things I tried for thin lining did bugger all because they were treatments to improve blood flow. Which didn't do anything for me personally because my lining didn't have enough oestrogen
These included: l'arginine, high strength vitamin E, baby aspirin, vaginal viagra, red raspberry leaf tea and acupuncture
For other people these work wonders
For me, I needed oestrogen tablets to thicken up my lining
We used them to great success in my second IVF cycle - which nearly didn't proceed to transfer like my first because of thin lining
Lining improved from 5.5mm to 8.5mm in three days
My Dr said we could use this in a natural cycle but it would have to be a monitored cycle so as to introduce it at the right point, once the dominant follicle has grown to a large enough size that the oestrogen won't block ovulation. You'll also need a trigger shot to make sure the follicle releases
Progesterone after ovulation will help keep the lining plump and receptive.
All questions to ask your Dr xxx