Frontline didn't work for me either and I was very diligent. I found out at the Vet - my girls had fleas, I was dumbfounded! The house had fleas, the yard had fleas. It was awful! The Vet said "welcome to Florida!"
I used Capstar immediately to get rid of the existing fleas on Cassie & Reba. Bathed them and tried Advantix (didn't work either) Called the lawn guy to treat the yard. Vacuumed house daily. Sprayed Zodiac flea stuff on carpets and soft furniture. Laundry was done daily. Checked them often with flea comb. (Drown the ones I found in Dawn). Still had them. I was living, breathing, sleeping flea control.
Switched to Trifexis after 6 weeks of the above. No more fleas!
You may need an antibiotic for secondary infections as well as an alternative preventative. I think you need to see your Vet.