If you're concerned about price, you should be taking the generic equivalent for Claritin. I can get that at Costco for $11.xx for a bottle of 300 pills (one pill a day, so that's about 10 months of it.) But if it doesn't work, it doesn't work. Zyrtec has not only gone OTC, but it's also gone generic, making it quite affordable. Try that before you start taking someone else's prescription.
You might need to add a decongestant to the antihistamine, if you have a lot of sinus congestion. Try it with your Claritin to see if it works, if that's your problem.