Just to clarify, because everyone here is suggesting cranberry juice-- UTI's feed off sugar, so you need to get the *straight, unsweetened* cranberry juice. Often it's sold in concentrate form. Here's the deal with this, the straight cranberry can also give someone a sore stomach because of the acid content, so use thoughtfully.
Kids often aren't great at describing where exactly their aches are. Bladder infections do hurt, and a child this age might call it a tummy ache because of the location on the body. (No child has ever told me they had a bladder ache!) It's really hard to know.
You might consider getting your daughter to urgent care. This may have nothing to do with toilet training; she's may have got some bacteria caught in the urethra and the doctors will be able to give you antibiotics and pain relief medication. (There is an OTC for pain relief, but it's for adults, not children, and does mess up the urine tests, so do not give her any pain relief until this is figured out.)
I think you just have to listen to your mama instincts. If you feel she's got a UTI, take her in ASAP, because these can develop into kidney infections. And not to be snide, but your husband might have to just get over it...you aren't the first parent to incur a medical bill because you had a concern which proved to be false. (I've worked forever with kids and have taken my son to the ER for what proved to be a cold, just because the symptoms were very troubling. $300 later...) Take good care and I hope your daughter is feeling better soon.