I have a much different answer.
You need to talk to your doctor no later than tomorrow.
Tell him about taking the antibiotic.
Do not continue any antibiotic on your own.
One pill never treats an infection.
You need to get help for the anxiety as well.
If your doctor is considering a scan, do it now so you do not keep worrying.
This will also show the extent of the diverticulosis.
In fact, diverticulitis can start just like this, and needs close attention....if you get worse pain, feeling hot, feeling nauseated, feeling ill....to the ER.
Continued pain is not normal, and not likely to be muscular localized to this area.
For diverticulosis you need a soluble fiber diet.
It should be cooked, and vegetable foods mostly.
Peeled and steamed veggies.
If this pain is getting worse..which you imply...to the ER for exam.
I am a double board certified US doctor, acredited by the correct board certifying US organizations, and have been a clinician for over 20 years.
Please click a positive.
Let me know if you have more questions.
By the way, you can save time and effort by requesting me specifically, in medical. I am here daily.