You have a flawed understanding of how your cells consume glucose.
Lactic acid it not produced in any significant quantity during 'normal operation' of your body.
Your cells break down glucose into a molecule called pyruvate in a process called 'glycolysis'. This yields some 'energy' (in the form of ATP). This process requires some energy, so the net gain is only two ATP. It also requires a couple NAD- ions, which pick up some spare hydrogen protons that get kicked out. Those NAD- get turned into NADH, are are used later in the process (and turned back into NAD-, so they can facilitate more 'glycolysis').
If the cell has enough oxygen, it can then oxidize the pyruvate in the Citric Acid Cyle (aka the TCA cycle, aka the Kreb's cycle), gaining many times more ATP (34, in total).
If, however, the cell doesn't have enough oxygen, it can't run the TCA cycle. This isn't a big deal in the short term. Your cells can keep running through that glycolosis process to produce energy as long as they have enough glucose to break down, and enough NAD- to grab protons. The glucose isn't generally a problem. Your body keeps a fair amount of it in the blood, and the liver can release more pretty easily.
The problem is the limited number of NAD- ions in your cells. Once those are used up, glycolosis stops. Fortunately, your cells can 'free them up' by using them to turn pyruvate into lactate. This produces the 'milk acid' you talk about, but it frees up the NAD- for more glycolosis. The cell hangs on to the lactate for a while in the hopes of getting more oxygen it can use to turn it back into pyruvate and run it through the TCA cycle, and if that doesn't happen, it eventually diffuses out into the blood where it ends up in the liver, which uses it to build up its glycogen stores for the next time there's a sudden demand for a lot of glucose.
So, in short, unless you're exercising hard, your body will have no trouble meeting its oxygen demand, and no lactic acid will be produced. This has been an overly simplified (but mostly accurate) description of this process. I'd encourage you to do your own research to learn more (the search terms 'cellular respiration' 'glycolosis' and 'citric acid cycle' should all be useful)