Husband is 40 and has a 3.1 prostate level withb psa test. Doc will retest in 6 months she says its high. Should we see a urologist before then?

Listen to your doc. One value for a psa (especially one that is within the range of normal) is not usually diagnostic. What matters more is a trend. If the value is still 3.1 in 6 months, it is reassuring. However, if it climbs significantly it may warrant a closer look.
A possibility. Many experts would consider a psa of 3.1 in a 40 y/o to be elevated and continued monitoring of the level is well advised. However, cancer is not the only cause of a high psa. Among other things, a second opinion from a urologist may help to detect an infection or infammation that needs more immediate treatment. Talk it over with your family doctor.