I had a claritin and then zyrtec 10mg. still have had allergies. can i also take a benadryl or allegra on top of those two to help?

No: The medications you list are typically taken as a single agent. If you are not getting any relief after several days of taking a single agent, adding an additional medication with similar effects is unlikely to help. At the same time you are at a much higher risk of experiencing serious side effects of the medication. Work with your doctor until you find a therapy that works for you.