Hi I'm 37y/o I Got Pregnant After 1st Try But

Hi I'm 37y/o I got pregnant after 1st try but miscarried in 7th week. I didn't have to have D&C. I use to have regular period 28d but since then I have period between 26-31 days. I keep trying to conceive but it is 6 months now and still nothing. I'm getting frustrated, especially because we got pregnant so quickly before. Any recommendation is it normal that my period is not like before? I went for ultrasound today (day16) and doctor said that I ovulated recently that she can see some fluid and remaining follicular (not sure if I remember it correctly). Not sure if you can tell how many days ago I ovulated? thank you Hana