Your cat is in heat! Wait a few days (don't let her out!) and then take her to the vet to be spayed.

 Also, it's possible she may be in heat. Don't let her outside.

 If she is having trouble going to the bathroom the Vet will probably want to administer enemas. My cat had a terrible time going to the bathroom and spent 3 days at the Vets with them applying enemas. Nothing worked. After $300 (altho the cost didn't matter) I poured about a teaspoon of mineral oil in the palm of my hand and offered it to her. Be careful that she doesn't sniff any of this up her nose when she checks it out. They usually love it. She went the next day and now I mix 1 teaspoon in her food once a week. No more than once a week though.

 Try taking her to the vet, also you could have then take a look at one of her fecil droppings. It might have to do with her anal glands, or she might be having problems going to the bathroom. But again ask your vet. -Good luck