Issues with cat in heat?

Okay so my cat is a stray that I took in a couple years ago when she was pregnant. She's the sweetest thing, but she pees all over stuff and I swear it coincides with when she's in heat. Is it true that cats pee all over things when they're in heat? And just out of curiosity, why doesn't she bleed when she's in heat? If I get her fixed will that solve peeing issues? She still uses her litter box too BTW. And does she have to be in a certain age range for me to get her fixed? I will choose a best answer! Thank you :)