My ears piercings get infected very easily, I've tried sensitive earrings & sterling silver but they infect my ear. Is there somthing else I should try?

Gold? Gold may help. Less likely to irritate and inflame your ears. "sensitive earrings" sometimes still contain nickel [and also depends on the quality of the outer covering]. Sterling silver has some copper in it [are you allergic to copper? ]. Anyway, gold might be an alternative - although $$$.
Infection unlikely. More likely to be a sensitivity to metal. They make some kind of guards for posts---they're plastic sleeves that go around the metal. But it may require a larger hole than you have. You could try coating the earring with vaseline or even Bacitracin before inserting it---this would give some barrier between your skin and the metal. And if it really is infection, Bacitracin would also help.