Tomorrow I'm supposed to get my period, but today I feel like I have c…

Tomorrow I'm supposed to get my period, but today I feel like I have cystitis. Today after urinating, I found blood, I thought it was PMS but I was wrong. When I had my first child, I learned that I was pregnant when I had cystitis. Now I don't know what to think. Girls, do you think every time I'm pregnant is it possible for such a thing, about cystitis?