Discouraged...

I’m 40. I will be 41 in less than a month. We’ve been TTC for a year now. I got pregnant right after getting off of birth control but then had a miscarriage with D&C at 9 weeks in March. Since then my period has been weird. I was very, very regular with 28 day cycles prior to the D&C. Now I can have a 33, 35, 37, and now longer cycle. I’m currently on day 39 waiting for my period. I’ve take pregnancy tests every other day since day 1 of missed period with all negatives. Not even a slight or faint line. I know I’m not pregnant. I’ve got no symptoms; only cramps as if I’m about to start but that’s been going on for almost a week now. I’ve got an appointment with a fertility specialist at the end of this month. My husband keeps telling me not to worry because of the appointment but I can’t help feeling defective. I don’t feel old at all but am I starting menopause? What is wrong with me that my body isn’t working anymore. I’m trying hard not to get discouraged but... anyone ever had anything even remotely similar?