Your avatar is very nice! Is your ID a typo? or did you intend it to be the
way it is? Just wondering.

Serious memory issues should be evaluated by a doctor.

But some things from your post stick out for me.

1) depression can cause this. It can really impair word retrieval, or time sense.
Your use of Adderall may be a culprit. Amphetamines over time cause depressive symptoms, esp later in the day when they wear off. There have been some studies showing the low zinc levels, reduce response to amphetamine.

2) Low Folate levels and low B12 can cause mental slowness, brain fog.
Methotrexate depletes folic acid severely, and you don't say if you had adequate folate support.

3) Other nutritional weaknesses can affect the brain. Essential fatty acids are needed by the brain to repair and keep neurotransmitter receptors working properly. Omega-3 nutrition is very very important.
this link has more:
http://neurotalk.psychcentral.com/showthread.php?t=6092

As it happens, zinc and EFAs work together for ADHD patients as well.

3) low levels of B6 and low tryptophan may cause low serotonin to be made in the brain, so if you are low in both, you may show depressive symptioms as well as increased responses to pain.

So you can try to improve your intake of these nutrients, but if you consider your mental problems as severe, it would be best to see a doctor.
Other diseases may present with confusion in the beginning. Parkinson's is one. Low thyroid is another.

Good luck.