Why Does One Have Periods Continuously?

I started taking Lisinopril 10 mg at the end of December for borderline high blood pressure. Since then, I have had a continuous period with extremely low flow (or you could describe it as two missed periods with 4 weeks of constant spotting.)

I am not pregnant, and just had a normal Pap smear two months ago, as well as a complete physical two months ago.

Is this something that is a rare symptom of Lisinopril? The timing is much too coincidental for it to be anything else.