Left breast swells at night then subsides a bit after i get up in the morning. could this just be fluid retention?

Unlikely: Unlikely. Fluid retention does not cause symptoms on one side vs. the other. My best guess would be some position in which u sleep causes some restriction of fluid outflow (lymph, blood). U could try sleeping on ur right side all nigh, by using a foam wedge, to test this theory. If its correct you should not have L sided swelling in AM, but may have R sided swelling instead.