I would say that even if you are remotely concerned get the cat to the vet ASAP.
Ringworm as Gillian says is not a worm and your cat being wormed will not stop it from getting ringworm as it is a fungal infection and highly contagious. You can catch it from an infected cat and pass it on and can spell disaster in terms of trying to get rid
.
In large colonies it is not unheard of for vets to advise a cull of all cats on the premises and burn everything to kill it out.
Otherwise you just have to keep treating and waiting until it eventually burns itself out.
If at all concerned though get in touch with your vet ASAP. Ringworm is highly contagious and shouldn't be taken lightly.
Let us know how you get on.
Hugs & Purrs
Sarah