Thanks for providing more information.
Upset stomach,diarrhea are listed side effects of Cephalexin and usually subside after stopping it.
Antibiotic usually kills good bacteria while fighting with infected bacteria resulting in disturbance in gastric flora and stomach upset.
So most likely your gastrointestinal symptoms are related to antibiotic use.
And loose stool once a day is not so concerning and it is advised to complete your antibiotic course as per directed.
In the meantime you should start probiotics containing lactobacillus acidophillus and eat yogurt.
Also hydrate yourself with plenty of fluids and oral rehydration solution.
Take OTC Motrin for pain.
Also take metamucil.
If your symptoms'll get worse over the time then consult your doctor for further evaluation and management.
I hope this helps.
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