It means that the given dose of letrozole is not sufficient for you. In this cycle with the given measurements, chance of conception is on lower side as there is no dominant follicle and endometrial thickness is also less.
Next Steps
As you are having pcos, lifestyle modification is required:
Exercise daily for 20-30 minutes
Take high protein diet like egg whites, sprouts, green leafy vegetables
Limit carbohydrates like rice, sugars
Take plenty of water 3-4 litres per day.
-In the next cycle you can start with higher dose of letrozole 5 mg from day 2-6 and go for follicular study. If there is dominant follicle and good triple line endometrium then you can try with same medication for 3-6 months.
If there’s no dominant follicle then along with letrozole, you have take injectables under doctor guidance.
Health Tips
Tubal evaluation with hsg test
Husband semen analysis is required