Bay Tree Leaves Dying

I have a bay tree standing approximately 6' (yes feet) tall it is shaped into a topiary tree. Now for my problem. Last summer I noticed that new leaves were starting to develop not a problem but it has taken them until now to fully emerge. Shortly after I brought the tree inside the leaves started to turn yellow and then to brown. No black blotches just yellow to brown and now they are falling off the tree. But the new growth is coming, but the old leaves just keep turning yellow. I am wondering if it could need repotting (urn is 18 inches or 45 centimeter in diameter and 15 inches or 37 centimeters deep). I haven't fertilized since last summer as I was told it needed to be dormant for the winter. Please help with any suggestions you might have. I love this tree and am losing all the old growth and having to cut off the new for shaping.

I don't know what you mean "by dormant for the winter". The plant just grows less under poorer indoor light conditions, but it does not go dormant. It needs less water when it is not growing much, but it must not dry out completely. Letting it dry out completely will kill a lot of the roots and to compensate the tree will drop its leaves to try to evaporate less water. You will have to let the new growth stay at least on most of the branches so that the tree has something to photosynthesize with. Later you can cut back the branches a few at a time to get it back into shape.
I hope your urn has a good drainage hole in the bottom. When you water, the soil should be completely wetted and after the excess drains out the bottom, this drainage water should be at least occasionally thrown away to prevent salt build up.
Repotting once a year just as new growth is starting is a good idea. The old soil may be depleted, too acid or too compacted. If the urn does not have good drainage repotting is essential, because the soil will have way too many salts in it by now.