Blood after sex

I have been married for a month, I have been using this app to know when is safe to have sex without condoms, in my opinion is very useful. Last night, after sex I found blood, I didn't found in my panties, just when I used the toilet. Is that normal? Last night was the second time that I have blood after sex. My period will be next week, so, I don't think that this is the reason. Someone can tell me if that is normal?