Not Peeing?

Hello we have a 18 week old german shepherd named bella.

Over the past 2 days we have noticed some weird things she is doing. She will whine at the back door and we will let her out like usual but she squats 4-5 times around the yard. I am not sure if she is actually peeing as her back has been to me every time this has happened. My husband took her to a friends house and said she did this same odd behavior today but this time he said he never saw anything come out. Then this evening before we went to bed bella started dry heaving in the bathroom. My husband quickly put her in shower and she stopped but then she crawled under our bed and vomited under the bed. We went to bed around 11 and at 12pm she peed in our room. This was a shock as she had been outside at 10 and peed and pooped, she also has been house trained since she was 10 weeks. About 2 am she started crying under the bed and I let her into our bed thinking she isn't feeling good and would love some TLC. She started whining like she wanted down so I put her down and instantly she peed again... Even in the 10 minutes it took to write this I had to let her out 4 times and each time she has squatted to pee and nothing. Her other behavior is fine she still plays and eats/drinks fine. My husband thinks that maybe she has crystals in her urine so he game her a vitamin C tab at dinner because that's what the vet prescribed for his last dog.

Anyone know what's going on? I am getting nervous that something terrible is wrong...