Crying for no apparent reason

I want to know why my 5-year old just cries out of the blue. She complained of a toothache the other day, I’ve tried everything the doctor told me to do and it seemed to work the day after. But the next day, it’s back to where we started, even though I’ve done everything exactly the way I was suppose to just like the day before. I am getting extremely frustrated because her whimpering and constant crying is annoying me and even if I can’t do anything about it, she won’t stop crying. At first I did think it was because of her toothache but other things just get her crying and I’ve even tried comforting her by holding her, laying in her bed until she falls asleep, and I’ve even given her more attention than my younger child. I don’t know what to do anymore.

It’s gotten to a point where, it’s really close to Thanksgiving and if she is going to continue having these sudden outbursts of crying, I can’t take her to the dinner. I don’t want to deal with family asking every minute what is wrong with her when I can’t even find out what is wrong myself. I’ve tried talking to her asking what is wrong, but she just shrugs her shoulder and says I don’t know. That just frustrates me more.

Please tell me if I am just over reacting on a situation that I am suppose to be comforting her in or am I assuming the worse and just frustrated because of her constant crying and not knowing what is going on with her.

Thank you and I am hoping to get an answer soon because the crying and the whimpering is short-circuiting my patience fuse.

Thank you!