Generally the appearance of a specific symptom in an isolated incident like this is suggestive of an emotional issue (not a pro opinion). If you are extremely depressed, the chemicals in your brain do not develop as often or as well, so you have less to work with. In order to provide essential functions to the body, the immediate defence is to remove whatever isn't needed for survival - in some cases, it's memory.

Talk to your doctor, definitely. If this IS the case, likely you have a simple chemical/neurotransmitter imbalance that can be easily and quickly corrected with a prescription.

Until you talk to your doctor, I suggest activities that increase the brain's "happy chemical" and keep it up - like a hobby which absorbs your focus for hours while stimulating the brain. Reading, sewing, etc...whatever you like. See if it makes a difference for your memory. If it does, designate a specific amount of time each day to commit to that (or similar) activities, in order to re-create the brain's need to release those chemicals regularly.

Consistency & self-discipline will definitely help. I know it can be difficult to gain the motivation at times, but it's worth it. You are worth it.