High PSA

Hi,
I'm 32 years old, I Had a urine infection from 2.5 month the doctor ask for many tests (Urine test, blood tests, PSA...) the result was infection but the doctor couldn't know the reason and the PSA was 18 and the prostate was 42mg.
the doctor gave me antibiotic for 1 month, after 3 days of the antibiotics I felt good. I repeated the tests after 5 weeks, every thing went normal including the prostate size, but the PSA went down to 10, the doctor said it needs timeto go back to the normal, now I did it again mean after 5 weeks from the last test and the PSA is 7, as I know it must be less than 4 in my age.
It is normal now to have PSA 7? how much it will take to go to less than 4? or there is a problem and I have to be checked?
Thanks you very much for your kind help, hope hearing from you soon.

Best Regards,
Sam