I was also riding with no or almost no pressure. Put on the HD adjustables. 4 bolts, even I could change them. Much better ride. And you can buy them online discounted and no tax and free shipping from Kutter and other HD dealers. Should have done it sooner.I've had the same problem since day 1 with my '11 Ultra. Had it checked with no trouble found. Finally said eff it and ride 0 pressure.
Some times there are no bubbles as most guys expect to see. But a fuzz leak. Have to really look close at connections and seals. Can be very hard to spot. Looks like tiny fuzzy bubbles in soda, best I can describe it.That was done on mine several times and not a bubble formed. The next day, zero PSI in the shocks.
Replace the shrader valves. That is the valve where you add air. The rubber seals on those valves wear out. For bikes that have internal pumps to air them up then the seal on the pump is probably leaking. Either way the inside pressure should hold the valve closed.