40 with Irregular periods

I have an 18mon old and my periods have always been on the dot regular until this year. In February I went 70 days without a period then suddenly went back to normal and then now in August I hadn't had a period until last week but I'm not even sure it counted. I started taking an OTC fertility drug that's supposed to regulate your hormones and after 4 days of taking it I got a dark reddish brown "period" that was enough when wiped but never really needed a pad for. only had it for 3 days (normal period is 5 days) . I had my hormone levels and had an intervaginal Ultrasound in April and everything looked OK. Anyone else had this happen to them and still got pregnant without any major costs/ fertility meds?