Can we go for IUI or direct IVF. Months.

Hello, we have been TTC for 5 months and have been regularly timing the intercourse with follicular scan . My wife had a low AMH when did for the first time which is 0.43 and then repeated again a month later it was 0.89 and when did couple or days back it was 1.2. The first two were done with home collection and last one was done in lab setting at lalpath labs. The follicular scan revealed 2 dominant follicles on right side every month and the endometrial lining was on average of 11.8 cm when ovulation happened and gynec said the ovulation happened really nice and she said it's unlikely that AMH can be this low which is when we tested and got the result to be 1.2. So now she is suggesting for IUI for this month and has given letrozole to induce ovulation . HSG showed no blocks. My sperm count is 75 million with progressive motility of 41% and morphology of 3%. So should we go ahead with IUI or try naturally or directly go for IVf since we have been trying close to 6 months .