My little female dog ( I know I will spell it wrong) chiwawa is in heat. And my large german shepard is going crazy! What do I do? I have tried to separate them but it does no good. The large dog crys and it is not fair to my little dog. Her name is bella and the large dog is crash. How do I stop crash?

I am scared that he will hurt her!

KEEP THEM APART! It doesn't matter how much they cry. AND you get both of them fixed as soon as possible.

What isn't fair is your female dying from him trying to mate or her giving birth.

Edited to remove need to move question to proper board.

Umm lets see a female Chihuahua getting pregnant by a German Shepherd, and you are afraid he will hurt her...

I am going to apologize in advance because this is going to be harsh.

Why to you have two UN altered dogs in your house? You are obviously not a breeder of either one seeing as you can not even spell the breed of your dog correctly.
Secondly your female, Bella, will die. If not during the pregnancy, which is almost 99.9% inevitable, she WILL die after birth. Oh and if my some miracle of a chance she does survive, she and most likely her puppies with die of Mal nutrition while she is nursing. She will not be able to provide enough nutrition to feed even ONE German Shepherd puppy let alone a litter. Do you see why it is SO important to keep them separated?
Fix them ASAP. Millions of dogs die each year to neglectful pet owners and back yard breeders.

Separate your dogs NOW. They are going to cry. Especially him. He's completely love sick.

These animals need to be fixed. It's easier on you. Its easier on them. And it will make everyone happy. If you'r worried about cost.. Contact the shelter in your area and ask if they know of any low cost spay/neuter clinics. You can fix him now. He will settle down within 2 months and become very relaxed. You can spay her when she is a month out from her heat cycle. You can spay her now, but it is an extra charge. Its not necessarily more dangerous, its just because the vets need to do a little bit extra to make sure everything is tied off correctly.

He will more than likely break her back and kill her trying to mate. Her breed is very fragile as it is.. and males dogs in lust are not gentle, not even to the females their own size.

Do the right thing.

Just to reiterate what others have said, you need to keep them separated for the duration of her heat.

A dog heat lasts for 3 weeks in total, the first and second weeks contain obvious signs such as bleeding but the final week of heat your little Chi may not have any signs at all, it is VERY important to keep them separated for the entire 3 weeks.

At my house we have a 2 door rule... if there are dogs that are aggressive towards each other, or a dog in heat there must be at least 2 closed doors between them at all times, that way there can be no accidents, even if one managed to sneak past one of the doors.

Once her heat is over you can get her spayed. It can be done right now but the risk is a little higher as she is bleeding more. Spaying is a common practice and when done by a good vet carries little risk.
For females recovery is usually good with most being back to their old selves within a week or two.

For your Shepherd you may want to consider getting a family member or friend to look after him for a few weeks until the Chis heat is over, or putting him in a boarding kennel.
He will miss you yes, but it's better than having him pine over your female constantly and driving himself (and you) crazy.

Oh, an I remember the spelling of Chihuahua by sounding out the name in my head funny... Chi-Hu-a-Hu-a, just remember there h's and you should be able to remember the spelling ;)