My cat isn't pooping other than little bits and idk why

I took her to the vet and and turns out she had worms and stuff in her ear so we are giving her medication for that like metronidazole twice a day and oridermyl once a day and she also is constipated after we changed her litter too a new one she never used before and this is the third type of litter she tried and she never had any problems with changing litter she used to do her business as usual and we also tried feeding her zucchini and carrots boiled cuz I found out it helps with constipation in cats and we also with the recommendation of the vet gave her glycelax but she still isn't pooping but she's still playing and being normal and is only peeing she's about 6 months I really don't know what to do id appreciate any help thanks